My friend made a stupid mistake selling a car.

Hello together, in advance it’s not about myself but about a friend of mine. He sold his car recently. Everything went quickly without a purchase contract. He received the money, had the ID card shown briefly, the picture compared then the car was charged in a registered condition and away he was. The buyer said he reported the car and sent the signs to, he did not make of course. My colleague then to his insurance, case sign ert. The insurance only meant that is not her problem in such a case he is obliged to pay 3 months further because they do not let him out of the contract. When it turned out that the identity card was faked (he had called the competent authority for the address) he went to the police. He has cell phone number from him and the guy is also available. He wanted the police to locate him by cell phone location. But do not make as long as he does not But has the buyer not already committed a crime by the wrong ID card???? How can my colleague now unsubscribe the car, as said there is no purchase contract, no signs, no papers! I am grateful for any help.