She was assessed a two-shot penalty for the infraction, and two shots for signing an incorrect scorecard. An email from a television viewer during Sunday's final round alerted officials to the violation committed Saturday, and the tour confirmed it with video review.
The viewer contacted European Tour officials to explain that Harrington had marginally knocked his ball forward while replacing his marker during the opening round. "I had no idea that I had replaced my ball in the wrong place".
As awkward as the situation was, it could have been worse: If golf officials hadn't made a rule change a year ago, Thompson would have been disqualified entirely. Now, because her incorrect score resulted from a failure to include a penalty she wasn't aware of, she wasn't disqualified.
"It's unfortunate what happened", Thompson said afterwards. So you're telling me that's a fair situation as well? I didn't realize I did that. "But I just wanted to play my game and have a strong finish".
It turned out that a television viewer had spotted something that had happened on the 17th hole during the third round.
Thompson, who was reduced to tears, was two shots in the lead after playing 12 holes at the time.
Thompson fought to control her emotions after a brilliant second shot on the 18th, as the crowd rallied behind her and chanted her name.
A bogey on 15 put her once again on the back foot, and she missed an eagle putt on the 18th for the outright win - instead forcing a play-off with Ryu.
House sends bill to Trump blocking online privacy regulation
The move would allow them to compete with the likes of Google and Facebook in the lucrative digital advertising market. During floor debate, she said, "Republicans want this (private) information to be sold without your permission".
"Every day is a learning process", Thompson told ESPN after her loss.
"He'd best be [on top of his game], otherwise I'll be in the kitchen making sure if they go a bit flat, we're not going to be happy", Willett said " I'm sure that he's been practicing since he came out [to the course]".
When she was informed of what she had done by an official, she responded by saying "Is this a joke?"
Lexi Thompson was on course to win the ANA Inspiration for the second time to claim her second major title as she was leading by three shots, but things did not go as planned for the 22-year-old.
McIlroy decision to play golf with Trump, whose statements about women have raised eyebrows, contrasted sharply with his own pro-women stand against members of Muirfield golf club in Scotland who disapprove of allowing women members.
Thompson's support extended to the digital realm, where Tiger Woods immediately offered his thoughts on Twitter.
Russell Henley made 10 birdies in the final round, rallied from a four-shot deficit and closed with a 7-under 65 to win the Shell Houston Open and earn the final spot in the Masters.
Far different from Mickelson's plight is that McIlroy is still only 27 and there are plenty of Masters ahead of him.