Explored Valut 22 w/ Boone tonight for the doc at Camp McCarran... After going through all of the first four levels, I take the elevator to level 5 - Pest Control, exit the door, and ED-E is there even though I did not have him with me (he is a companion though, left at my hotel room in Novac). He doesn;t follow me, but is just there. Anyone else see this? I figured it may bebecause he's important to the history of this Vault, but I cannot get anything from him.

Actually its because for some reason the Vault 22 Elevator seems to have a automatic "moveto player" command attached to it.
A lot of people on the PS3 and Xbow360 use it as a means by which to get back lost companions whenever they randomly disappear.

Thanks. I'll keep that in mind if I ever lose a companion. (PS3 by the way).

Def. I believe this is prob one of the most dependable ways to get any lost companions back without resorting to loading previous saves etc. I think there are a few other places like it but so far I only remember Vault 22.