What's the average amount of money lost at any one time?

Not counting unclaimed estates, 'buried treasures', etc does anyone know how to find out the average sum of lost money floating around at any one time. Just simply monies that have fallen out of pockets, handbags, dropped accidentally, thing like that. I'm curious about both the average amount in the U.S. and then the whole planet. And I'd love to know, if you answer, were you got the info from because I'm very interested in odd, random facts like this. Obviously. Thanks!