After completing ED-E's side quest i thought it to be a good idea to try out the new equipment. I huffed it over to vault 34 thinking whats better than a vault full of ghouls? well, this was where things started going wrong.

I left Boone outside due to the rads, and brought ED-E in with me, needless to say ED-E was knocked unconscious within moments. I waited till he came back and he was knocked out again. I left the area expecting to see him pop up, only to find Boone and no ED-E.

I have revisited every area Ive been to in hopes of him popping up, i have also waited/slept for 3-4 days hoping he would come back.

Has anyone had this problem or found a workaround?

hes prob with you i have been walking around and npcs talk like hes right next to me so i think hes just invisible... im also at ceasars tent and it says i have to leave my companions outside and i cant leave him outside when hes invisible....

yea i ran into a similar problem, had to reload a save earlier than the vault, i couldn't finish the "nothin like a hound dog" quest since i couldn't boot him.

Ive had this problem, apparently from what ive read on yahoo answers, this is a pretty big bug.. you lose those fallowers, and you have to restart, do the missions with out them... I just lost boone, im sooo [censored] done with this game, 20 hours into it, and im done.. so [censored] done..

I didn't have a human follower but what happened to my Ed-E was that he got stuck at a doorway. It literally looked like the clearance height wasn't high enough and he just kept hitting the top over and over again. I didn't want to reload because my last save was 15-20 minutes prior and vault 34 was kinda kicking my butt so I told him to leave. On his way out, the ghouls killed him and I was forced to reload from an earlier save. Sorry to hear about you guys losing followers there...