When you go to see Mr House at the casino and your told to go up to see him alone, i left boone and went up, but coming down he was nowhere to be seen?

This happens with a few companions sadly.

If your playing on PC you can use the console commands to teleport him back. Otherwise you can try waiting a few days in hopes that he returns to lucky 38.

maybe you can send him back before going to house and pick him up later ? next time you get there?

Well i'd already gone up without him thinking he'd be waiting for me but was he balls. I'm on 360 so no commands
I loved that guy

I've heard that there's a glitch whereby you take the elevator in vault 22 (I think that's right - the vault you go to for the "there stands the grass" quest) to the bottom floor and for some reason your companion's there waiting for you. I haven't tried it personally but other forums have this posted and people have replied saying it works. The only other advice has been to wait a couple of days, but that's not guaranteed.

[Edit] Vault 22.

I have a similar, but actually worse problem with ED-E: i havent lost him, he always is next to me when i go from one area to another but he does not move. Ever. Ive tried kicking and getting him again, telling him to wait for me somewhere then picking him up again, nothing seems to work. Its not that big of a loss, cause with Boone we can usually kill anything w/o many problems, but i'd still rather have ED-E with me. Console cant really help me, any ideas would be appreciated. (btw i think it has to do with the vault 22 problem, cause he is doing is from around the time we were there, not sure tho)

Something similar has happened to me. In one game save I lost boone, he was no place next to me and after waiting for about 7 in game days with no return I reloaded a previous save. I then went to the Gun Runners location, turn around, and see boone running in the opposite direction away from me. I tried to talk to him and he would respond while sprinting... so I followed him running for about 15 minutes. After seeing him attacking random mobs while not responding to me, we finally reached some odd ball location.... he just stood there. I fast traveled to a different location... he didnt come with (to busy standing I guess). So after seeing that, its possible in my opinion that he may have just decided to ditch you and never come back. This issue might have something to do with the AI follow command that the companions have. Seems to me that boone thought I was someplace else, and when he got there he was pretty convinced that I was right in front of him.

I had something like this aswell with Boone. Ported from Novac to Ranger Stat C., looked around, no Boone, reload, teleport again and i see him running back towards Novac (super fast), i followed him, but halfway he turned around and everything was back to normal. Guess i got lucky that time.