I was standing in a big crowd during a concert on a street in São Paulo, Brazil. My friend was in front of me, looking in the same direction. A guy came from behind, shoulder-checking me. He said "sorry" and stood on my left. I instinctively patted my pockets, to find the right one, where I keep my phone, empty. I looked at the guy who passed me and he said "look, there are some children running away from here, maybe they have your stuff". I looked around and didn't see anyone running though. A few seconds later my friend pointed at the ground and showed me my phone lying down there. There's no chance it fell out, I was standing still in fairly tight pants.
Also, few minutes later, I saw a credit card lying down on the street, as it turned out, it belonged to a woman standing next to me.
I'm quite sure the guy who passed me was trying to rob me. Is it a common/well-known strategy of pickpockets? Is there some sensible purpose to throw stuff on the ground (to pick it up later when I leave?), or is it possible he simply panicked and dropped it?