Man that sucks, it does look like something fell on it to me. Wasn't it in your MIL garage for the winter? That's the first suspect I'd have....
I had to change the battery and it's right there in that quarter, I would have noticed. (It was my first thought though)
The three dings are in a row, one is right up in the middle on the panel in front of the trunk, so not just something that bumped into it. I think someone whacked it with something. I vacuumed it last week, including the trunk, it had to have happened after that.