Carrier/rack problems of the 2017 Mercedes Benz CLA250

I was driving on the toll road when out of no where I here a loud boom and crackle above my head. Almost like a firework when it goes off. I thought it was a gun shot. When I looked up my panoramic sunroof was gone. Nothing was driving in front of or beside me. Nothing hit my car. However mercedes says it's impossible and something hit it, but my insurance won't pay for the sunroof repair because of class action lawsuits. They say it is mercedes responsibility. However, mercedes basically called me a liar and refuses to replace the panoramic sunroof. They want to charge me $3200 to repair it.