I'm with GoneWestUtah. I once went for a coffee with someone and we sat outside. I ordered a small cake as well and set it down on the table next to the coffee. I nipped inside to use the bathroom and when I came out, my cake had completely disappeared!
It wasn't long before we found the culprit - a crow sitting in the tree above us! He had my cake under his left foot and was picking bits of it off to eat, whilst staring straight at us.
Apparently, whilst I was inside, my friend had also nipped in to ask the waitress something and left our coffees and cakes unattended. Mr. Crow must have been watching...you can't get anything past them and they do have an eye for shiny things, Duke, so there's merit to Utah's idea