After double checking breakers... If you are comfortable doing so, kill the power to the RV, take the cover off the breaker panel and check the connections at each breaker. While you are in there, tighten them up. Before closing it up, re energize the system and check for power at the outgoing side of the breaker to that circuit - BE CAFEFUL!
First step after that is: recheck your work on the replacement GFI outlet. Make sure it's wired properly.
Second, grab a meter or test light and start walking through the system. First place I'd check is at the GFI outlet to see if there's power there. If not start walking though the system until you find power.
Other than what's been mentioned, I can't imagine there's any hidden breakers. The outlets are daisy chained, and some are used as junction boxes so it's possible a connection has come loose. NOTE: just because you test an outlet and it has power, don't assume that location isn't where the problem is. Power going into that location doesn't mean power is going out of that location. You might find it wasn't a bad GFI after all.
The attachment may help even if it isn't your exact year and model.
Good luck. Electrical problems can be a pain, but if you carefully walk through the system, you should be able to locate the problem. Again, be careful when testing.
Tom and Pris M. along with Buddy the 17 year old Siamese cat
1998 Safari Serengeti 3706, 300HP Cat 3126 Allison 3060, 900 watts of Solar.
Dragging four telescopes around the US in search of dark skies.