Normally, if the damage is on the rear of your car, odds are they'll put the guy at fault. But since theres no police report, it gets tricky. Call your agent ASAP. If youre ever in an accident thats somebody elses fault ALWAYS call the popo. You don't have to make a claim if you don't want to, but if you choose to do so, you'll be a lot better off with a report to back you up.