Lexi Thompson gets 4-shot penalty, loses major after viewer tip

RANCHO MIRAGE, Calif. -- Lexi Thompson had no idea why LPGA Tour rules official Sue Witters was approaching her on the way to the 13th tee at the ANA Inspiration.

When she found out, Thompson still couldn't believe it.

A television viewer's email had alerted officials to a day-old rules violation by Thompson for a 1-inch ball placement error . Her three-shot lead had just been wiped out by a four-shot penalty.

"Is this a joke?" Thompson asked Witters.

For the third time in less than a year, a major title was decided by an oddly timed assessment of a penalty, this time costing Lexi Thompson four strokes from a previous day's infraction.

Lexi Thompson lost her three-shot lead thanks to a penalty…