Slide out floor parting from frame

If the screws into the wood floor were rusted away, I'd suspect the water travelled laterally back into the plywood quite a ways and the floor is pretty much shot and in need of replacement. Not an easy job but not impossible. Probably plenty of uTube vids out there with one being close to what you need to do. Your experience underscores why it's so important to keep the caulking on all exterior seams in good shape. When it fails, water will get behind the trim and find it's way into the wood. So many older RVs stink of must and mold because water got behind the exterior trim that's at floor level and water has seeped through at the wall/floor seam, soaked the bottom of the wall and the floor plywood and started the mold growth there. Best stuff I've found is gutter/flashing sealant from Home Depot. Comes in several colors including clear.