In my case, it was an Easter buffet at a hotel on the San Antonio riverwalk, and I was hosting 3 of my college friends.
We were the last guests, and when we decided to get dessert, they bussed our table and took the ladies purses to the register.
To be clear, our table was 15’ from the dessert table, and te room was completely free of obstacles to LoS. They SAW us at the dessert table getting dessert and still did that BS. In fact, we could see them at the register with the purses, waving us over.
After I had words with the manager, we got fresh drinks & cutlery to eat our desserts and the women got their purses back.
For me the worst service I've ever seen was at a restaurant at Mammoth Mountain. This was back in the late 80's and three families, mine, my uncles, and a family close to my step-father were all there, so it was like 15 people and kids.
We were seated in a section around the corner in the restaurant, because the main area was full. As you'd expect in a large group, a lot of conversation happened. After we were there for a very, very long time talking, we became aware that nobody had come to take our orders for drinks, let alone dinner, so someone went to talk to the staff. A little while later the waitress scurried up and said, "I'm so sorry. We completely forgot you guys were here."
After we got our drinks and she came back to take orders, my turn came up. I asked for a steak. She then asked me if I wanted soup or salad with it, and I said I'd like a salad with tomato, bell pepper and onion. She replied that they were out of bell pepper, so I said okay, then a salad with tomato and onion. That was when she said, "We're out of tomato, too. Come to think of it, we're also out of lettuce." Well, no salad.
When the food arrived it was on plates that were hot. She announced that we should be careful, because the plates were hot at the exact same time she handed the plate to my 8 or so year old cousin who promptly dropped the plate onto the table, because it was HOT. I can't remember if there any further snafus, but that was enough for me to rate it number 1 out of my 3 worst service experiences.