Welcome to the forums!
So, yes, I guarantee that someone has had mystery floor damage due to a leak from roof, vent, window, door, sink, plumbing, waterlines, tanks, etc..
The first thing you need to figure out is whether your damage is old evidence of a leak, that has already been repaired, or evidence of an active leak where the floor is still regularly getting wet. You might try hosing the trailer down and making sure that you don't get water inside the trailer, then thoroughly test the plumbing to determine if water is leaking from any of the water lines, run water into your grey tanks and flush the toilet into the black tank and so on. If you can convince yourself that you have neither an internal or external leak, you can focus on deciding whether your floor is damaged enough to warrant a patch.