What Do You Do?

Dilemma. What do you do if you find a $20 bill in front of your door and perfectly center between your neighbors' doors on either side? Could it be the neighbor on the right who dropped a twenty or the neighbor on the left or neither? Do you keep the money or would you ask your neighbors if they lost a twenty? But how would you be able to verify whose twenty it was? What would you do?

This is the dilemma I'm facing at the moment. I feel a bit guilty pocketing the money, but I'm not sure what I should do. Once I found ten bucks on the sidewalk and felt like a thief for taking it, though I was extremely thankful to the stranger who paid for my meal.

Anyone encounter a similar situation? What did you do?