I recommend you go back to Nellis, and find Ed-e, if possible.
My Ed-e got KO'd in the Hoover Dam battle, I had a bit of a search finding him.
If you are willing to not have a creature companion for a while, talk with the robot Victor outside the Lucky 38 and choose ok to making your companions wait.
Then activate your human/mutant/ghoul companion if you have one and tell them to follow.
Waiting companions return to where you found them after a certain amount of time passes.