Go back and park in the same spot, then hide in the bushes. It may take a little while, but they'll be back, and will probably hit your car again. When they do, jump out of the bushes and run at the van yelling and screaming. They'll probably speed away. So, you'll have to do it again. This time, when they hit your car, jump out and get the license plate number. Wait a few days, park in the same spot again, but this time hide in a different bush. When they hit your car, jump out and yell "I got your license plate number bitch!".
They won't hit your car again after that.