I have posted about this before.
I was walking along when a man run in front of me and jumped the school fence (this was 16 odd years ago, when schools were less secure). A second man chased after him… stopped, shouted a question to me (“what road are we on?”). I told him, then he said, “Police”, flashed a warrant card (could have been his Blockbusters Video card for all I knew), and asked if I had a phone. I passed mine over (why, just why?), and he made a couple of calls, with no answers, then said, “I have to take your phone.” He then run off with my phone, and jumped the school fence, disappearing from view.
At this point I realised I’d just been scammed.
Only, I hadn’t been. My phone was returned that night by a uniformed officer, with a bag of stickers, etc. for my kids. I have no idea how they traced me.