McDonald's

Today 1/17/19 at 7:03am I went through the drive through window at store #7663. I asked how much was the order behind me and that order was like $6.65 and I told the gentleman in the window I would like to pay for that order. When I was retrieving my order from the next window I saw the guy in that vehicle hand the gentleman in the window payment. When I paid for the extra order I didn't receive a receipt. When getting to work the guy, who I paid for, jokingly said I should of paid for his order and I informed him that I did. He looked in his bag and realized he didn't get a receipt either. I called out to McDonalds and talked to a young lady named Dedrus (not sure how to spell it) and she said there was no way that happened because once it is paid it goes out of the computer and maybe I paid for the car behind that vehicle. Seems unlikely since both totals that each of us paid was exact. I usually go to this McDonalds almost every morning and sometimes at lunch, but will not be going there anymore.