Golf-Fan favorite Thompson says will learn from heartbreaking defeat

(Refiles to correct headline to says, not say)

By Rory Carroll

SAN FRANCISCO (Reuters) -Lexi Thompson admitted it was hard to smile after a painful back nine collapse at the U.S. Women's Open on Sunday, but the American fan favorite said she would learn from the experience and come back stronger.

The overnight leader had her second major championship in her sights with a four-stroke lead after her first nine holes, but her tee shot on the par-four 11th found the Olympic Club's thick rough and she could only manage a double bogey.

She lost her lead with a bogey on the par-five 17th and left a par putt short on 18 that would have put her into the playoff with Japan's Nasa Hataoka and eventual…