I told ED something to wait for me at goodsprings before i went fast traveling so he wouldn't get destroyed by the enemies. i came back to goodsprings later, only to NOT be able to find him after an hour of searching.
anyone might have an idea as to what happened? i really really miss ED's little battle anthem
btw, this is the 360 version, after the first patch.

My companions get lost or run off all the time.

so is there anything i can do to find them easily? i'd really hate to start a new game. :/

sometimes he will head back to primm. look in the house you found him in.

nope i didnt find him, but i appreciate the advice. xD

Try to wait three days then it should say something along the lines of ED-E returned to primm