Vending Machine Suprise

At my highschool we have 2 soda vending machines, and after lunch I wanted a soda. So I walked over to the vending machines and swiped my card. However it just spit out a dollar bill and denied transaction. So I tried again. Nothing. So I move to the second one and it goes through. I checked my account to check my money and it took the 2.25 it costs, so that dollar bill was just a surprise XD. Soda and a dollar :D