If he dies, he's gone forever unless you use a save. That goes for every character in the game that can die, which is the vast majority of them (NPCs critical to the main story just go unconscious, but I've only come across two of those, one being Amata at the start in Vault 101). But if you accidentally leave him somewhere using the "stay" command and you forget to pick him back up, he'll eventually go back to Vault 101 on his own. Or should, at least.
Question to those who are past GNR:
I just found the
Headquarters, entered the mainframe computer room and it (awesomely) marked the locations of the other
in the game on my map. I'm just wondering if I can safely visit them without screwing up the main quest if I haven't done the Rivet City stuff yet.