When I was in college I learned a valuable lesson. Someone tapped me from behind on my way to work one morning. We both stopped and my car had no visible damage so we didn't exchange information and the other party drove away. Then my car would not start. It turned out that the tap had messed up the carburetor float and it cost me a few hundred dollars but I had no recourse to the party that hit me since I didn;t have their information. Slightly different from the OPs situation, but nonetheless a valuable lesson for me.