The man had come through the drive-thru and used his debit card to purchase his items. I handed receipt and card back at same time, gave a friendly smile and thank you, have a good day and come again and he was happy as he was pulling away. Ten minutes later, a not-so-happy man knocks on window and as soon as I opened it he loudly and sternly demanded I give him his card back. I said, "sir, I do not have your card. I handed it back to you along with the receipt." I also said, " you placed both items on middle console, if that helps. Maybe they went between console and passenger seat or the console and the drivers seat..." He said he searched everywhere and he was embarrassed at gas station because I took his card and put it in my pocket. I assured him I did not. So he said, "well you have it or you have it to somebody else and both of y'all are thieves." He demanded my name. So, smiling, from ear to ear, I gladly gave my full name because I know I'm not a thief and I know I gave him his card. He said he was going to the authorities right then. I simply told him I was sorry he was inconvenienced, and assured him he was wrong in his accusations and requested he have a wonderful day. After another 10 minutes of his absence, the store received a phone call and the person asked to speak to me...I already knew who it was before taking the call. He apologized to me for being so rude when I remained calm even through his accusations of calling me a thief. He said when he got home and parked in driveway, when he opened his door, his debit card fell onto the ground...the next time he came to sonic, he gave me a $10.00 tip. And if he sees me in other places, he still apologizes and sometimes pays for my drink at store or wherever we may run into each other.