Yeah, this camper has always had a tarp on it when stored, and was also put away with the nose higher than the low point drain corner, and that's the way the water ran....right down the back wall.
Its doubtful a pressure test would have found this as the screw was one of a number holding the awning mounting in place and was drilled into the centre piece of 3 laminated 2X2's across the rear. As far as I know, a pressure test only works around the cut-outs for windows, vents and things like power cord boxes, etc.
It's really too bad as this is the last 9'6" camper Interior RV ever made and should have been a collector's item. However, it will be better than new once it's repaired and again, we're very thankful we had insurance and that they came through for us.
You can see here the rear roof is virtually non-existent.
This is a shot looking down from roof into rear wall.