Accident with hitchhiking expert report insurance refuses

Hi, in the fall I parked in a parking garage. When I come back my driver’s door is damaged. Next to me is a BMW X5. Wheelbase, entry angle fit exactly. Driver escape? Because the BMW X5 has fixed plastic on the wheel boxes, you can see nothing with it. With me is sand dust to see and the paint scratched. Can it be that a solid Kunsstoff on wheelbox has no traces, although the nevertheless sensitive paint has scratcher? After long waiting I have everything with In the evening, after work, I went to the police because of the advertisement. Damage according to the workshop 1000,- Euro. The opposing insurance (Kravag) commissioned Carexpert with an expert report. The expert looks at it. After that the insurance registers and says according to the expert report it could not have been the X5. I demand the expert report. But the insurance does not let me see it. What would you do? Many greetings!