RANCHO MIRAGE, Calif. – A stunned Lexi Thompson received a four-stroke penalty walking off the 12th green Sunday at the ANA Inspiration. LPGA officials received an email from a viewer about a possible rules infraction during the third round when Thompson was on the seventh hole of Round 4.

Thompson lost the tournament on the first sudden-death hole to Soyeon Ryu.

Officials deliberated for two hours before informing Thompson that she had replaced her ball an inch away from its original position on a 1-foot putt on the 17th hole Saturday. She received two strokes for that violation plus two more for signing an incorrect scorecard. Her third-round 67 was changed to a 71.

“Oh my God,” Thompson said, walking to the tee. “This is ridiculous.”

“Is this a joke?” she asked.

LPGA rules official Sue Witters later said she was 100-percent certain that Thompson did not do it intentionally.

“It was a hard thing to do. To be honest, it made me sick.”

The LPGA said she breached USGA Rule 20-7c and Rule 16-1b. She incurred an additional penalty for incorrect scorecards under Rule 6-6d.

In a matter of seconds the tour’s top American went from a two-stroke advantage over Suzann Pettersen to a two-stroke deficit.

A teary-eyed Thompson pounded a drive on the 13th tee. Showing incredible mental fortitude, Thompson went on to birdie the hole, while Pettersen bogeyed.

Thompson, winner here in 2014, joined four other players – Inbee Park, So Yeon Ryu, Minjee Lee and Pettersen – in a tie for at 13 under with four to play.

The USGA’s proposed rules changes for 2019 would prevent such a thing from happening in the future because of the reasonable judgement standard. Thompson made a reasonable effort to return the ball to its original position.