Of an acorn falling from tree in campground and blowing a hole through lid on vent fan in bathroom. Well that is what just happend to me. How hard are those to replace? It has the brand name Ventline ...
Sounds to me as though the vent lid had accumulated enough sun damage to have become brittle, so for what it is worth, it was soon to shatter or turn to dust on you anyway. You got a couple weeks less use from it that it would have otherwise rendered.
And yes, pretty easy to replace. Ditto Ed's recommendation to add one of those housings, too, while you are up there. Those things are worth their weight in gold.