You're leaving a hospital after visiting a friend. Just as you're walking out the door, you see a crumpled $20 bill on the ground. You're surrounded by people, but no one is paying attention to you, and it is unlikely anyone would notice you pick it up.
Do you swoop down and pick it up, or do you just leave it there?
Or do you pick it up, wave it around, and yell "Did anyone lose $20?!" and wait for someone to claim it?