Why is this creepy?
The winner can't miss the fricken GPS chip in there, right? It probably comes with a note too. Instead of the winner making a call, they come to you, instead. Don't worry, they won't bust down your door or anything. They're not 5-O. Jesus!
If I was working at a shopping mall or something like that, I would weigh every single chocolate bar and see if there's a difference in weight. Then split the $10.000 with someone else (because they are not allowed to participate in promotional events). A metal detector may work too, since they're bound to have some metal - like circuitry, the antennae, the battery, etc.