Now, if this had been a problem with him alone, I would have posted this in the corresponding thread but...
I decided to just keep going with the mission. Helped Huleeya (sp?) get rid of the bothersome fools, and exited the tavern. I checked that he was still with me, and since he was, I decided to do a little test, and went back into the tavern. Just as I had predicted, he also dissapeared, since he wasn't in the previous cell either. I did this test a third time going in and out of the foreign quarter's second floor, and he also dissappeared.
So, I really have no idea what could be causing this, so I'm gonna need a bit of help.
Here's my mod list (it's from the ini therefore not in the correct order):
[Archives]
Archive 0=Morrowind.bsa
Archive 1=Tribunal.bsa
Archive 2=Bloodmoon.bsa
[Game Files]
GameFile0=Beryl's_Head_Replacer_v1.0.esm
GameFile1=Better Heads Bloodmoon addon.esm
GameFile2=Better Heads Tribunal addon.esm
GameFile3=Better Heads.esm
GameFile4=Bloodmoon Landscape Overhaul 1.0.esm
GameFile5=Bloodmoon.esm
GameFile6=Book Rotate.esm
GameFile7=GDR_MasterFile.esm
GameFile8=Hilgya the Seamstress.esm
GameFile9=Morrowind Patch v1.6.5-BETA.esm
GameFile10=Morrowind.esm
GameFile11=Texture Fix 1.8.esm
GameFile12=Tribunal.esm
GameFile13=Animated Morrowind 1.0.esp
GameFile14=AtmosphericSoundEffects-3.0-Tribunal.esp
GameFile15=BTB - Alchemy.esp
GameFile16=BTB - Settings.esp
GameFile17=BTB - Spells.esp
GameFile18=Better Bodies.esp
GameFile19=Better Clothes Complete (BTB Edit).esp
GameFile20=Better Clothes_v1.1.esp
GameFile21=Better Skulls.ESP
GameFile22=Bloated Caves.esp
GameFile23=Book Jackets - Bloodmoon - BookRotate.esp
GameFile24=Book Jackets - Morrowind - BookRotate.esp
GameFile25=Book Jackets - Tribunal - BookRotate.esp
GameFile26=Book Rotate - Bloodmoon v5.3.esp
GameFile27=Book Rotate - Tribunal v5.3.esp
GameFile28=DB_Attack_Mod.esp
GameFile29=DM_DB Armor Replacer-ExpRanks.esp
GameFile30=DN-GDRv1.esp
GameFile31=Daggerfall Collection Ver 1.1.esp
GameFile32=GCD Restore Potions Fix.esp
GameFile33=GCD_SS_patch.esp
GameFile34=Galsiahs Character Development.esp
GameFile35=Graphic Herbalism.esp
GameFile36=Illy's Solsteim Rumour Fix.esp
GameFile37=Immersive Chargen.esp
GameFile38=Improved Hand to Hand.esp
GameFile39=J-ninja_v.1.0_m.esp
GameFile40=KS_Julan_Ashlander Companion_1.3.esp
GameFile41=Key Replacer Trib & BM.esp
GameFile42=LGNPC_AldVelothi_v1_20.esp
GameFile43=LGNPC_Aldruhn_v1_20.esp
GameFile44=LGNPC_Aldruhn_v1_20_suppl.esp
GameFile45=LGNPC_GnaarMok_v1_20.esp
GameFile46=LGNPC_HlaOad_v1_32.esp
GameFile47=LGNPC_IndarysManor_v1_51.esp
GameFile48=LGNPC_Khuul_v2_20.esp
GameFile49=LGNPC_MaarGan_v1_20.esp
GameFile50=LGNPC_NoLore_v0_83.esp
GameFile51=LGNPC_PaxRedoran_v1_20.esp
GameFile52=LGNPC_Pelagiad_v1_30.esp
GameFile53=LGNPC_SecretMasters_v1_30.esp
GameFile54=LGNPC_SoulSicknessPatch_v1_00.esp
GameFile55=LGNPC_TelMora_v1_20.esp
GameFile56=LGNPC_TelUvirith_v1_20.esp
GameFile57=LGNPC_VivecFQ_v2_10.esp
GameFile58=LGNPC_VivecRedoran_v1_50.esp
GameFile59=Lgnpc_SN.esp
GameFile60=Mashed Lists.esp
GameFile61=More Better Clothes.ESP
GameFile62=Morrowind Battle Cry.esp
GameFile63=New Argonian Bodies - Clean.esp
GameFile64=New Khajiit Bodies - Clean.esp
GameFile65=Nymeria's Faster Walk.esp
GameFile66=Painkiller's Lucky Coin.esp
GameFile67=Psy_VivecGodReplacer.esp
GameFile68=Psy_VivecGodReplacer_Tribunal.esp
GameFile69=Quieter_UI_Sounds.esp
GameFile70=Scripted_Spells.esp
GameFile71=SirLuthor-Tools.esp
GameFile72=Soti_KungFu.esp
GameFile73=TLM - Ambient Light + Fog Update.esp
GameFile74=TLM - External Lights Ownership.esp
GameFile75=TLM - Light Sources (Clearer Lighting).esp
GameFile76=TLM - Light Sources (Lanterns).esp
GameFile77=TLM - Light Sources (Natural Water).esp
GameFile78=TLM - NPC Light Sources.esp
GameFile79=The Gambler.esp
GameFile80=UFR_v2_ADDON-Rings.esp
GameFile81=UFR_v2_ADDON-Robes.esp
GameFile82=UFR_v2_base.esp
GameFile83=Undead - Mummies Arise from Death.esp
GameFile84=Undead arise from death 2.0.esp
GameFile85=Undeads - Skeletons Arise from Death II.esp
GameFile86=Undeads Skeletons Arise from Death.esp
GameFile87=Vurt's Grazelands Unique Trees.ESP
GameFile88=Vurt's Solstheim Trees & Bushes Replacer.ESP
GameFile89=WA_Signy_Signposts(!).ESP
GameFile90=Westly Presents_Exiles of Akavir_N.esp
GameFile91=Westly's Master Headpack X.esp
GameFile92=Westly_Presents_FCOT.esp
GameFile93=Windows Glow.esp
GameFile94=abotWhereAreAllBirdsGoing.esp
GameFile95=improvedbound.esp
GameFile96=k_sneakrest.esp
Archive 0=Morrowind.bsa
Archive 1=Tribunal.bsa
Archive 2=Bloodmoon.bsa
[Game Files]
GameFile0=Beryl's_Head_Replacer_v1.0.esm
GameFile1=Better Heads Bloodmoon addon.esm
GameFile2=Better Heads Tribunal addon.esm
GameFile3=Better Heads.esm
GameFile4=Bloodmoon Landscape Overhaul 1.0.esm
GameFile5=Bloodmoon.esm
GameFile6=Book Rotate.esm
GameFile7=GDR_MasterFile.esm
GameFile8=Hilgya the Seamstress.esm
GameFile9=Morrowind Patch v1.6.5-BETA.esm
GameFile10=Morrowind.esm
GameFile11=Texture Fix 1.8.esm
GameFile12=Tribunal.esm
GameFile13=Animated Morrowind 1.0.esp
GameFile14=AtmosphericSoundEffects-3.0-Tribunal.esp
GameFile15=BTB - Alchemy.esp
GameFile16=BTB - Settings.esp
GameFile17=BTB - Spells.esp
GameFile18=Better Bodies.esp
GameFile19=Better Clothes Complete (BTB Edit).esp
GameFile20=Better Clothes_v1.1.esp
GameFile21=Better Skulls.ESP
GameFile22=Bloated Caves.esp
GameFile23=Book Jackets - Bloodmoon - BookRotate.esp
GameFile24=Book Jackets - Morrowind - BookRotate.esp
GameFile25=Book Jackets - Tribunal - BookRotate.esp
GameFile26=Book Rotate - Bloodmoon v5.3.esp
GameFile27=Book Rotate - Tribunal v5.3.esp
GameFile28=DB_Attack_Mod.esp
GameFile29=DM_DB Armor Replacer-ExpRanks.esp
GameFile30=DN-GDRv1.esp
GameFile31=Daggerfall Collection Ver 1.1.esp
GameFile32=GCD Restore Potions Fix.esp
GameFile33=GCD_SS_patch.esp
GameFile34=Galsiahs Character Development.esp
GameFile35=Graphic Herbalism.esp
GameFile36=Illy's Solsteim Rumour Fix.esp
GameFile37=Immersive Chargen.esp
GameFile38=Improved Hand to Hand.esp
GameFile39=J-ninja_v.1.0_m.esp
GameFile40=KS_Julan_Ashlander Companion_1.3.esp
GameFile41=Key Replacer Trib & BM.esp
GameFile42=LGNPC_AldVelothi_v1_20.esp
GameFile43=LGNPC_Aldruhn_v1_20.esp
GameFile44=LGNPC_Aldruhn_v1_20_suppl.esp
GameFile45=LGNPC_GnaarMok_v1_20.esp
GameFile46=LGNPC_HlaOad_v1_32.esp
GameFile47=LGNPC_IndarysManor_v1_51.esp
GameFile48=LGNPC_Khuul_v2_20.esp
GameFile49=LGNPC_MaarGan_v1_20.esp
GameFile50=LGNPC_NoLore_v0_83.esp
GameFile51=LGNPC_PaxRedoran_v1_20.esp
GameFile52=LGNPC_Pelagiad_v1_30.esp
GameFile53=LGNPC_SecretMasters_v1_30.esp
GameFile54=LGNPC_SoulSicknessPatch_v1_00.esp
GameFile55=LGNPC_TelMora_v1_20.esp
GameFile56=LGNPC_TelUvirith_v1_20.esp
GameFile57=LGNPC_VivecFQ_v2_10.esp
GameFile58=LGNPC_VivecRedoran_v1_50.esp
GameFile59=Lgnpc_SN.esp
GameFile60=Mashed Lists.esp
GameFile61=More Better Clothes.ESP
GameFile62=Morrowind Battle Cry.esp
GameFile63=New Argonian Bodies - Clean.esp
GameFile64=New Khajiit Bodies - Clean.esp
GameFile65=Nymeria's Faster Walk.esp
GameFile66=Painkiller's Lucky Coin.esp
GameFile67=Psy_VivecGodReplacer.esp
GameFile68=Psy_VivecGodReplacer_Tribunal.esp
GameFile69=Quieter_UI_Sounds.esp
GameFile70=Scripted_Spells.esp
GameFile71=SirLuthor-Tools.esp
GameFile72=Soti_KungFu.esp
GameFile73=TLM - Ambient Light + Fog Update.esp
GameFile74=TLM - External Lights Ownership.esp
GameFile75=TLM - Light Sources (Clearer Lighting).esp
GameFile76=TLM - Light Sources (Lanterns).esp
GameFile77=TLM - Light Sources (Natural Water).esp
GameFile78=TLM - NPC Light Sources.esp
GameFile79=The Gambler.esp
GameFile80=UFR_v2_ADDON-Rings.esp
GameFile81=UFR_v2_ADDON-Robes.esp
GameFile82=UFR_v2_base.esp
GameFile83=Undead - Mummies Arise from Death.esp
GameFile84=Undead arise from death 2.0.esp
GameFile85=Undeads - Skeletons Arise from Death II.esp
GameFile86=Undeads Skeletons Arise from Death.esp
GameFile87=Vurt's Grazelands Unique Trees.ESP
GameFile88=Vurt's Solstheim Trees & Bushes Replacer.ESP
GameFile89=WA_Signy_Signposts(!).ESP
GameFile90=Westly Presents_Exiles of Akavir_N.esp
GameFile91=Westly's Master Headpack X.esp
GameFile92=Westly_Presents_FCOT.esp
GameFile93=Windows Glow.esp
GameFile94=abotWhereAreAllBirdsGoing.esp
GameFile95=improvedbound.esp
GameFile96=k_sneakrest.esp
(If there are any mods that could cause other type of problems, also let me know, please)