What Jerry says is interesting, but if he lost 1 leg, I would assume he's reading that off his CMP. So that would really mean 1 leg of the 50amp service.
That being said, if he's just guessing meaning part of his coach (or 1 leg) is out, then perhaps it is one of the breakers. I had this happen on my '99 and not all the power was out, just in the kitchen and I believe the TV, basically the passenger side of the coach. I thought it was a ground fault and replaced the outlet, but no luck, then went looking for breakers in the basement and found them on the back wall (in mine the tanks are behind that wall) and the breakers were just inside my 2nd door on that wall or even on the ceiling I forget now. I could see that one was reset, so I switched it back on and everything was fine.
We blew the breaker using an electrical heater (that's not normally used) along with perhaps the instant hot water.
Mike