Never actually caught anyone, but one time at the Gold Coast Casino in Vegas, I had a good dealer. Someone brought up dealing from the bottom of the deck (not in a bitchy way) and the dealer asked the rest of us if we minded taking a quick time out. We all were mostly just having a good time, so nobody said no. He just wanted to challenge us to see if we could catch him dealing incorrectly. He even called the pit boss over and cleared it with him first. He was damn good, that's for sure. Admittedly, when i play ring at a casino, i'm there for fun, so i'm drinking, so take that into consideration from my end. Only 2 guys said they could tell when he dealt from anywhere from the top, and he said only 1 of them was right. The pit boss could tell (well, no shit right?) every time and dealer confirmed. Was a cool experience and I could only tell how/when he did it when he slowed it way down and had us lean in.
So, when i play live, i kinda check for it, but figure if they're actually good at it, i'm not likely to catch em. Only brought this up as I thought it was a cool experience.