Ok, this is gonna sound stupid, but where do party members go after you separate from them?

I temporarily let go of ED-E and it said he went back to Primm, however now I need him again and I can't find him in Primm (I expected him to be in the room I activated him in, but he doesn't seem to be anywhere else in town either). The same goes with Raul at Black Mountain; I sent him back and he isn't in the room I found him in.