I helped free an Argonian slave while I was doing a quest for one of the Imperial Guilds(I always mix up the Legion and the Cult) I was trying to free some redguard or something from a rogue Ashlander camp but stumbled across some pages to an Empire book that was useless and so happpened to stumble across an Argonian. He said he was a slave so I freed him and he wanted me to escort him to the Argonian Mission in Ebonheart. We start walking and head to Suran. I completely forgot about him and went back and saw he got ambushed by dragons cliff racers. I stabbed them to death with my spear. When we got near the entrance to Suran, I put on my Boots of Blinding Speed and left him in the dust. I took the Silt Strider to the town closest to Ebonheart, which wasn't really close. However he didn't spawn with me. I shrugged and went to Ebonheart anyways, I figured he would teleport if I went into a cell via door or something. I enter the Mission and no Reeh-Jah. He disappeared somewhere...

I've tried backtracking but I've honestly lost him. He's nowhere to be found, but if my journal is any indication, he's still alive.(I assume if he did die I'd get an update in my journal)

How can I get to this guy? I guess I had Skyrim on the mind when I figured that companions had the same following logic. I waited 3 days in Ebonheart, hoping he'd find his way but nope. I thought for sure entering a door would teleport him.

Any suggestions on how to find this guy?

Non-modded followers don't have any following AI aside from follow the player, so if you get too far away, they'll stop in their tracks and wait until you get close to them again. If you don't mind getting your hands dirty with some console commands, you can pull him to you:

Write down the numbers these three commands return:

player->GetPos x
player->GetPos y
player->GetPos z

Then use these three commands with the numbers you got previously:

reeh_jah->SetPos x
reeh_jah->SetPos y
reeh_jah->SetPos z
reeh_jah->enable
reeh_jah->disable
reeh_jah->AIFollow player 0 0 0 0

That *should* warp him to you and make him follow you again. If that doesn't work, you're going to have to track him down. Sorry.