We have a 2007 HitchHiker II which we keep under a good shed, but not enclosed. We have towed it over almost the entire lower 48. One morning I was walking behind the RV, when I thought I was stepping on gravel that shouldn't be there, but looked up and saw the large back window shattered. There was probably as much broken glass on the outside as on the inside of the trailer. We jumped to the conclusion that someone must have slipped up thorough the woods behind our house and shot a BB or 22 rifle. We called the police who filed a report and then had to special order that entire back window frame. I don't remember exactly but it was over $1000 just for the window and frame. We had it replaced at a local RV center.
The discussion on this thread makes me consider the possibility that it was not vandalism, and could have been some kind of spontaneous break. Of course, we will never know, but I have no reason to think anyone would want to do such an act of vandalism. We acted in entirely good faith, and our insurance covered the cost of replacement.
Frankly, I hope this theory of "unexplained broken window" is correct.