I had a situation a few years ago driving down a highway at night when all of a sudden I noticed a weird "thing" in the sky in front of me. It got closer and I swerved, but not enough to avoid it hitting the side of my car, taking off the side mirror and gouging up the front half of the drivers' side. Then I realized it was the plastic bed liner of the pickup truck in front of me that became unattached at highway speeds and flew into the air like a kite. My car was still operable, and I had a (poor quality, especially at night, but operable) dash cam, and the truck ahead of me didn't stop, so I sped closer to close the distance to the truck and for assurance, read out the license plate number aloud so the dash cam's microphone could pick it up before pulling over.
Contacted the police, took them about an hour to respond, and the officer gave me his email so I could send him the video. It was hard to make out but you could definitely see the object leave the truck, and a few seconds later appearing in my view, and me swerving.
Contacted insurance, they arranged the repairs, and I was out the deductible. About a week later I got a call from the police saying they looked up the plate and lo and behold, it wasn't even registered to a white pickup truck, but a blue sedan, so the plate was either stolen or swapped from another vehicle, at which point there really was no recourse.
Long story short, even if you have a dash cam, sometimes you're SOL. I _did_ use that as an excuse to upgrade my dash cam to one with better quality and night vision, but yeah, shit happens, and if nobody got hurt sometimes you gotta just accept it.