What should I have done?

I got off from work at about 6:15 pm yesterday and stopped at our neighbourhood Walmart on my way home to get some groceries. Spent about 20 minutes in the store and I have to say that for the amount of stuff that I bought, a US$100.18 bill is not too bad.

Anyways, I was pushing my cart across the pavement to where my car was parked when the wheel of the cart rolled over a piece of paper, folded in half. I almost didn't notice it since I was trying to decide what to make for dinner once I get home. I did a double look at that paper and could not believe my eyes! I looked around the parking lot, there was a few cars but there was no one in sight. I didn't pass anyone coming into Walmart as I was leaving either. I stood over that piece of paper for about 5 minutes trying to decide what I should do.

Figured that even if I take that piece of paper to Walmart's customer service, their employee(s) would probably claim it anyways. So, after much thought I picked up the piece of paper and pocketed it. I still have not decided what I want to do with it. Wanna know what it was? US$100!! If it were you, what would you have done?

P/S: I am contemplating going back to Walmart when I get off work today to see if anyone ask about that money. I don't feel right about keeping it (I could definitely use an extra $100) so if no one claims it, I am going to donate it to charity.