When I went to Boulder City, Lt. Monroe wasn't there. Just... gone. The console was no help. I tried (in no particular order):

player.moveto 0010c6de

prid 0010c6de then moveto player

prid 0010c6de then disable then enable

Nothing works. When I use the command to move him towards me, or for me to teleport to him, for the latter I get put in some random spot, with him nowhere to be found. When I did that I assumed he was glitched in the air or below ground, so I turned off collision. Not in the air or ground, just mysteriously vanished.

This is one of the oddest things I've seen in this game. Not even my Ol' Reliable, the console, can fix it. I deactivated all my mods and he still wasn't there.

Try using the kill command then try disable, enable then moveto.

Maybe he's already dead. Try the resurrect command first then disable, enable, then moveto.

What mods are you using? It's possible that some monster mods spawn things that wipe out entire towns including quest givers.

FalloutNV.esm
HonestHearts.esm
OldWorldBlues.esm
LonesomeRoad.esm
GunRunnersArsenal.esm
CaravanPack.esm
Caliber.esm
CFWNV.esm
Military NV Backpacks.esm
More Perks.esm
More Perks for Honest Hearts.esm
More Perks for Old World Blues.esm
More Traits.esm
NVInteriors_Core.esm
NVInteriors_WastelandEditonAWOP.esm
CaliberXgunrunners.esm
CaliberXhonesthearts.esm
Primary Needs HUD.esm
Arwen_NV_Core.esm
NVInteriors_Urban_Edition_AWOP.esm
AWorldOfPain(Preview).esm
IWS-Core.esm
IWR.esm
The Mod Configuration Menu.esp
DarNifiedUINV.esp
CASM.esp
GoodspringsSewer-1.22.esp
Wasteland Defense.esp
NewStripMapMarkers.esp
Arwen_NV_Realism_Core.esp
Arwen_NV_Hard-Core.esp
Arwen_NV_Med-Tec.esp
Light My Flare.esp
NewVegasBounties.esp
NewVegasBountiesII.esp
More Perks Update.esp
More Perks for Honest Hearts Update.esp
More Perks for Old World Blues Update.esp
More Traits Update.esp
Desaturated Cateye.esp
pipboy2500_edisleado.esp
PortableCampsite.esp
Sprint Mod.esp
BearTrap.esp
Improved Throwing1.esp
turrets.esp
QS_Blackwolf_NV_Backpackmod.esp
KDS Wearable Backpacks.esp
FlashlightNVSE.esp
Military NV Backpacks - BumBagUseSlot1.esp
AWOPCaliberXAmmoPatch.esp
AWOPLowLootGeneral.esp
AWOPLowLootMWeapons.esp
AWOPLowLootSkillBooks.esp
Realistic_Repair_NV.esp
Stealing -1 Karma.esp
aaaJNFSniperZooming.esp
dD - Enhanced Blood Main NV.esp
dD-Reduced Ragdoll Force.esp
dD-Smaller Spatters Realistic.esp
Dynamic Quantity Prompt.esp
Faster Terminals.esp
HonestHeartsCheats.esp
HJLLessDismembermentAndExplosionsv100.esp
WeaponModsixpanded.esp
WMX-Arwen_NV_Realism.esp
WMX-ModernWeapons.esp
WMX-HonestHearts.esp
WMX-OldWorldBlues.esp
WMX-LonesomeRoad.esp
WMX-PreOrderPackCaravan.esp
ServiceRifleReflexSight.esp
New Vegas Error Corrections Reduce CTD - NO DLC.esp
OverTheShoulder.esp
XP_Sound.esp
CFW-LR.esp
CFW-HH.esp
CFW-OWB.esp
CFW-GRA.esp
removechal.esp
WMX-AWOP.esp
WMX-AWOP-Overhaul.esp
WMX-MW-GRA.esp
WMX-GunRunnersArsenal.esp
WMX-ArenovalisTextures.esp
Expensive3.esp
Survivalist'sRifleFix.esp
The Weapon Mod Menu.esp
IWS-Core-Guards.esp
IWS-Core-Patrols.esp
IWS-Core-Civilians.esp
IWS-HH.esp
IWS-OWB.esp
IWS-LR.esp
Fellout.esp
NoQuestItems.esp
More Mentats.esp
IWR - Rebuilt.esp
HZSmoothLight.esp
Total active plugins: 99
Total plugins: 99

Even if he was dead, the console should still move his body right to me.

What's weirder is that when I try to move to him, nothing happens; I get transported to where I was standing. It's like my console is bugged or something

If the game de-spawns him after he dies then you won't see him at all.

Did you try these commands in this order?:
prid
kill
resurrect
disable
enable
It could very well be a mod that is messing with this particular npc. You do have IWS. Are you using any monster mods? I've used them in the past
and a overpowered radscorpion completely wiped out goodsprings including quest givers.

Just curious. Try starting a new game just to see if you can move to LT monroe or if he can move to you. If he's still gone then it's probably a mod.

I'll try that when I can, thanks.

But I deactivated all my mods and it still didn't work when I tried. We'll see. I'll get back to this thread.

If he is gone/dead/disabled/glitched then disabling mods won't do anything since the damage has already been done.

I finished the LT Monroe quest but he was missing from my game too. He wonders over to camp hope after so he probably died on the way.

This is the order of commands I used to get him back:
prid 0010c6de
enable
resurrect
kill
disable
enable
resurrect

He spawned right where i was standing in camp hope. Hope this helps.

Damn, that didn't work. Any other ideas?

Make a new save with all your third party mods disabled. You can leave the DLC stuff enabled.
Upload the save to hotfile.com. You can message me the link.

Nevermind, I got it working. Here's what I did:

prid 0010c6de
resurrect
moveto player

And he appeared! Thanks for your help jasper, at least someone cared enough to respond here.