As one of the 3 individuals having a shot at that time, I can confirm the above. After taking the shot into his mouth, as well as the lemon, he swished it around in his mouth (like tasting wine), and made several interesting facial expressions before the liquid came out of his mouth. Obviously it did not suit his taste buds.
When the waitress came over as said "you again - I'm not cleaning up your puke this time", I'm sure she must have misunderstood the situation. I suspect she was terminated the next day for serving sub-par tequila.