possible hit-and-run? fear?

On Thursday evening, while reversing, my car automatically braked hard due to the distance sensor. I got out to see if anything had happened. The parked car was already far away and showed no signs of an accident. When reversing up a hill, the car sometimes brakes automatically.

Someone (I think) heard me slam on the brakes or saw me get out and called the police. After about 30 minutes, the police stood in front of me and asked what had happened on xxx Street. I explained. The police officer had photographed my car, measured it with a ruler, and said he couldn't see anything. He also couldn't see any damage or evidence of an accident on the other car. But the car is being inspected at a garage. He said, "Don't make a fuss, I'll get back to you on Monday. If it wasn't an accident, it's no big deal."

If it was indeed an accident, it's a hit-and-run. There are no scratches, paint marks, or damage on my car at all. But because I was scared, I also spoke to a lawyer. Has anyone had similar experiences? What could happen? Thank you.