I have 200 hrs on my game so far and 175 have been with ED-E and Boone. I was exploring the southeast area of the map, specifically the crashed vertibird site. I just killed the bots and got the special named weapon (forget what it was now) and since I play on hardcoe I had to switch some gear around so I wouldn't be overweight. I gave ED-E some gear and then headed off to explore. I hit the surrounding caves with ED-E and Boone in tow. I continued to play, roam and explore my way down to the river edge (blue paradise vacation rentals) and up to Cottonwood Overlook. It must have taken me an hour or two to get there from when the last time I interacted with ED-E and when I went to save (I use a 3 save, rotating system and save very often) I noticed ED-E wasn't with me. He hadn't been killed. I went to reload but since I save so often I didn't have a save that went back to the down vetibird site.
I back tracked everywhere I went and I couldn't find him. I checked the caves (Searchlight East Gold Mine and Fire Root Cavern) and didn't see him. I do have a bad habit of just running down a mountain side and leaving companions looking for another route down. So I went back to the mountain ridge to see if he was stuck and didn't see him anywhere. I checked all the submerge buildings down on the lake front and nothing.
Now this was all before the first DLC (Dead Money). For the longest I couldn't use Rex cause it still said I had ED-E with me. Once the DLC came out and it forced all companions to leave I was excited cause I thought ED-E would go back to Lucky 38 or Primm. Once I stared the DLC it said all companions were released and it said I lost ED-E's perk, but once I completed the DLC he WAS NOT at lucky 38 or Primm. Still nothing!
So with the latest patch I used the Companion Dismal terminal and still no ED-E at Lucky 38 or Primm.

I LOVED ED-E as a companion, especially paired with Boone, but I'm more upset at losing all the gear that I gave ED-E. I think he had at least 2 special named weapons!

I don't know what to do?

Any help or suggestions?

Well I hate the glitch (and encounter it often) where upon almost exiting the Presidential Suite at the Lucky 38, ED-E turns hostile and everyone else (Veronica, Cass, Boone, etc.) beat the crap out of ED-E until ED-E explodes into pieces. Have to reload - otherwise no more ED-E.

I dont play on hardcoe mode, however i did loose ED-E in the rocks over there once, i had to fast travel a few times to get him back.
and in my first play through he got stuck in the vault 22 elevator.but if if where in your situation i would go to the computer terminal next to the elevator on the casino floor of the lucky 38 and dismiss all companions. which pust them back where you found them so all you have to do is go get them back.

if you havent gotten to the lucky 38 yet then there is one attached to the gun runners kiosk.

That is bad. Poor lost ED-E.

I never put anything on companions in case they disapear or it goes wrong. I carry it all myself. Maybe you could try looking at each place you went when he was with you and if you see his name in the local map or world map he's there.

Or do what others said and see if using a dismiss companions terminal will force him back.

Maybe he's dead somewhere if it's on hardcoe.

I dismiss buggy companions at the safehouse so they don't go anywhere, but if they get lost I always use the dismissal terminal. I love that thing!

I've used the dismiss terminal at the Gun Runners and at the Lucky 38 and he still hasn't shown up at Lucky 38 or Primm. Like I said this happen almost 30 hrs of game play ago, so there's going back. I was hoping the dismiss terminal would fix it, but so far nothing.

- IF he got stuck somewhere he should still show up on my map, but I have backtracked to where he last was and I never saw him on the map.
- IF he got killed would it give me a notifcation of that? Say he got stuck in the rocks, then when I went into the Dead Money DLC (that's when he was first dismissed, but never showed up anywhere) would he attack raiders and such on his own or would/should he have just gone back to Primm or the Lucky 38?

I know he's probably lost for ever, but this was my first time on forum so I didn't know if anyone else had the same issue.

Thanks for all the input though guys.