I recruited Boone and kept him up until finishing his personal quest, then dismissed him to Novac. A few days later, I went to rehire him and I couldn't find him anywhere. Eventually I had to use the console command to move myself to his position and I found him lying dead under Dinky like he had fallen from the mouth.

I resurrected him and used him for a bit, then fired him back to Novac. I came back for him a few days later and he was dead in the same place. There can't possibly be any hostile creature killing him since Manny, nor anyone else in Novac, ever gets dies. If I dismiss him to the Lucky 38 he will remain fine.

I never receive a message saying that Boone has died and he's always in the same location under Dinky when I find him.

Is he scripted to somehow kill himself if you leave him in Novac too long or is this some kind of bug? If it's scripted, I certainly wouldn't expect this to happen after finishing his quest.

I've also asked over at http://www.newvegasnexus.com/downloads/file.php?id=44204's mod page.

Seems like a bug, but I've never had it in the countless times I've fired him. Seems like instead of spawning in the mouth he's glitching and spawning just outside it and falling to his death, though I'm sure that height is small and easily liveable, maybe he's falling from the sky - like the deathclaw glitch from Fallout 3.

Just keep him in the Lucky38 as a fix around.

I always take my companions back to where I hired them. Have you tried that yet? Strange bug, I'll have to be careful with my saves on that situation.