2. Lexi Thompson, 2017 ANA Inspiration
As she was walking off the 12th green during the final round of the ANA Inspiration, Thompson was informed by an official that she would be assessed a four-shot penalty – for replacing her ball in an improper spot on Saturday. It turned her 67 into a 71 and wiped out her two-stroke lead. A viewer noticed that Thompson had replaced her ball an inch away from its original location on a 1-foot putt on the 17th hole Saturday while watching the telecast.
After officials reviewed the tape, Thompson was assessed a two-shot penalty for putting her ball in the wrong spot (Rule 20-7c), and then a two-shot penalty for signing an incorrect scorecard (Rule 6-6d). She regained her composure to tie So Yeon Ryu, but lost on the first hole of a playoff.
The Rule was changed shortly thereafter, and Decision 34-3/10 (Limitations on Use of Video Evidence) is often referred to as the “Lexi Rule.”