If there is no GFI to be found, I would tag every dead outlet, kill the power to the entire 110v system, then one by one, remove each tagged outlet and inspect the wiring. Look close for any black char. Also make sure each connection is sound. Some RV manufactures use crimp connections, others use screw-tight connections. Make sure your connections are good.
After you checked all the tagged outlets, power-up and see if you did any good. Sometimes simply disturbing crimped connections will bring the circuit back to life. If that ends up being your story, you surely will want to reconnect every outlet with the screw terminals.
I strongly advise to check the outlet that your heater was plugged into first. Then power up and check the dead circuit. You answer just might be at that outlet. If not, then check all the other tagged ones.