What should you do if someone accused you of not paying for something you already paid for and they did not provide a receipt?

I was at a food court recently and went to buy something from one of the stalls. There was only one person manning the stall I bought my food from. I paid for my food using a 10 dollar note and waited nearby while the person was preparing the food. After he was done, he asked me for payment again. I told him I paid, but he insisted I did not. To give the benefit of the doubt, I checked my wallet again, and know for sure I paid because I had only 1 10 dollar note before the purchase, but no longer had it. I told him as such and he checked the cash register, but did not say anything about not having 10 dollar notes.

In the end, he let me go (with the food) as a queue was building, but the tone he used seemed to indicate he does not believed I paid. How would you have resolved the issue? I got away with it, but I think I only did so because a queue was building up.