['Last summer I stayed with a friend as I was nearly broke.  I went the store to get food and got back $20 extra in change from the cashier and ended up keeping the money.']
Oh wow, so it was extra money that was not yours?
Well last summer while I was staying with a friend I went to the store to get some food.  I got the wrong change back and kept the extra $20 cause I didn't have a job yet.