Legal Question in Insurance Law in California

The guy who kicked the ball committed the tort against you so he is responsible. The gym will probably not be held liable because they cannot be held to control an adult's intentional and random act like that (unlike, let's say, a pattern of people being assaulted in the parking lot and the gym knew about it). Your property damage insurance policy on the car could pay but they can go after the guy for reimbursement. That may or may not raise your rates. You should talk to them. Or, you can sue the guy in small claims court to get the money and bypass your own insurance company.

Even if what the guy did was not intentional, it was negligent at least or at most reckless, and he is still liable to you.