I work on a university campus, and I decided to try a new cafe/restaurant out for lunch. I'd been in there before a couple of years ago and remembered that there was a few different 'stations', each with a till. I'd often go to the sandwich counter and buy a sandwich and pay there.
I walked in, heading straight towards the sandwich counter but there were no sandwiches there, so I walked around the entire perimeter of the restaurant looking for the sandwiches but I couldn't find them. A member of staff then ran up to me saying I hadn't paid, and I was confused but it turns out that there was a till at the front door that I had walked past without realising, and it was a buffet kind of restaurant/cafe now where you buy a 'slot' (e.g. the lunch slot) and can eat whatever you want in the restaurant and cafe.
I felt really embarrassed and awful as she ran up to me as if I was about to steal something, I was already walking back towards the door. I have recently been diagnosed with coeliac's disease so eating out is something I already find stressful, and I wouldn't be happy paying for this kind of thing without seeing the food and that there's no chance of cross-contamination, etc. I wanted to see if there were any gluten-free sandwiches or pre-packaged food.
I ended up with a lump in my throat and almost crying, I think I was just having a hard day and it felt like the straw that broke the camel's back. I felt so humiliated and embarrassed that I had done something wrong.