Sorry about the car. That really bites.
It must have taken a lot of work to pick the rock up and bounce it on the car a couple of times. That tells me that the person(s) responsible aren't afraid of work. Too bad they lacked good judgement and were inconsiderate of the work that went into making the car what it was.
I hope that the police are able to apprehend the cretins responsible for this and that you are able to prosecute. They need to have their freedom to throw rocks revoked.
If it had been my car, I'd be seeing red and wanting blood, too. I'm thinking that mechanical castration would be both a fitting punishment and a public service. Clearly the shallow end of the gene pool needs a bit of cleaning up.