Rear bumper dissolves during the highway ride and deals damage

Hello, today on the highway the rear bumper of our S60 year 2002 solved itself and flew away. A passat drove in. Fortunately, nothing happened to anyone. Only the passat got some scratches. We called the police to record the accident. (I hate it if you have to listen to your own accident afterwards on the radio.) On Monday I will report the damage of my insurance. Can someone tell me if the purchase the new bumper can happen over all-round? Would you be reclassified in the insurance? (We had no damage to it before. I can’t tell if someone has put us on the parking lot.) Will our liability V also be reclassified due to the passat damage? Should we stay at the expense of the new bumper, where do I get a black painted bumper for the S60? If possible not at the pharmacy prices of the Volvo dealers. Thank you and Greetings! ra666ack