My Grocery Store Charity Dilemma

I have the worst luck at this particular grocery store in Somers Point.

The store itself isn't doing anything wrong, it's me! I've done everything from spilling and breaking things, to getting behind the slowest customer in the store.  My visit yesterday had a different twist to my on-going bad luck.

When I paying for my groceries, I decided to go with the 'cash back' option. I got my receipt, along with 20 bucks, and put everything in my wallet. As I walked outside, I saw an old man with a tin can collecting donations for his respective charity.   I knew I had an extra dollar in my wallet. So, without thinking I put in a dollar bill. When I got in my car and opened my wallet, I realized that I accidentally gave him the TWENTY dollar bill instead of the ONE dollar bill.

Do I go back and grab the twenty dollar bill out of the tin can, or do I just go home? I'm interested to read your advice.   Feel free to comment below, and then I'll tell you what I did.