Accident responder has suddenly “found” greater damage to the car

Hello all, my friend had a small crash yesterday (she slipped someone at a lower speed). Right after the accident, the accident opponent did not ask my girlfriend to get the police (I know it was a mistake), with the reason: “That only makes more circumstances and with my car (Opel Corsa B) you can see nothing anyway…” Today the man of the accident opponent ran then, the car is a total damage, because the tailgate is pressed in, the shock tan and the frame is warped… (can’t say anything about this man’s expertise…) How should I proceed now, since we have the assumption that someone here has damaged the car afterwards in order to cash as much money as possible? Who determines in such a case actually the expert? Am happy about every tip how to behave in such a situation.