A proper installation of an RV fridge completely seals the rear of the fridge (the cooling coil/combustion area) from the living area of the RV. This is according to the fridge manufacturer and is intended to keep combustion gasses out of the RV. However, this is not to say all manufacturers do this properly! If this is done properly, you shouldn't get propane inside the RV from a burner stuck on without being ignited. From your post it sounds like there was a LOT of propane inside the RV.
I had to remove the trim around my fridge for a mod I was making and noticed mine was poorly sealed at the top and had some gaps at the bottom. I had to seal mine up myself.
Steve
