We Saw a Montana a couple of years ago at our local dealer repair shop where the floor had been under muddy flood water for 3 days before they could get it out. I figured it would be ruined but the flooring was undamaged when they got it dried out.
I am told by the repair shop that the way the floors are put together at the factory is, the vinyl is laid down over the entire floor and then folded over the edges and tack down. Then the floor is laid onto the frame. All of this is done before any cabinets go in. Water should never reach the subfloor from the top.
Having been to the Montana factory that is not always the case.