I remember many years ago getting a random phone call from someone who claimed they were a detective investigating a case. The detective sensed my skepticism right away over the phone and suggested that I look up the phone number for his police department, and to ask for badge number ZZZ when I call. I called back, everything was above board, they came and interviewed me (they wanted to see if I still had something in my possession which I thankfully did), they made a mark on the item to indicate that they had seen it already and I never heard from them again. Though I wonder if they ever caught whoever it was that was using that item ...