I'd make sure no one nearby had dropped it. Sure, they could lie and say they did, when they didn't. But, there was an incident at the Wal-Mart here in town where a 9 year old dropped a ziploc baggie in the parking lot. It had $150 in it that he'd been saving all summer. The security cameras showed it drop, a college student walking by picks it up, puts it in his pocket, unloads his carts, gets in his jeep, counts the money and drives away. It was in the newspaper, the local tv news - the guy eventually turned himself in and returned the money. I don't think he was charged with anything, though last I had heard the prosecutor was still reviewing the case.