The police should have attended this accident if they had been called, and in fact they should have been called. Both drivers have a responsibility to stop, and give to each other their names, addresses, the registration marks of their vehicles and the names and addresses of the owners of their vehicles if different. If anyone is injured, they also have to produce their certificate of insurance. If you have not done any of these things, you must report the accident to the police as soon as practicable or in any case within 24 hours.
The police will now have lost the opportunity to collect much of the evidence (measurements, position of vehicles, road conditions, breath tests etc) but they can still follow up the offences of careless driving, and failing to give details. The fact that your friend was doing a 3-point turn does not mean he is at fault, If anything it should have made him even more visible to a careful driver, who would have stopped well clear of him.