Hello, I am a solicitor with 20 years experience. I will try to help you with this.
This sounds like an accident - quite likely negligence- giving the car owners the right to sue you for compensation. There is not an obvious crime that I can see here.
When did this happen and did the officer say what offence had been committed. It is unusual way for a police officer to behave he would normally deal with it there and then. Do you know how the uncoupling occurred?