Did i do something wrong? I feel kinda anxious about it

I went to McDonald's because i wanted fries. All is well until i got to the food handoff window. I say hello to the girl and she just looks at me. Ok... she comes back with my food and just thrusts it at me. I say thank you and she gives me a tight lipped have a good night. Did i do something wrong? I feel like i did or must have done or said something i dont know