The 16-year-old Wie made contact while hitting out of a greenside bunker at the 14th hole. The sand clearly moved, and the incident was picked up by TV cameras and tournament officials.
Wie didn't know about the penalty until she reached the recorders' office after her round at Royal Lytham. What she thought was an even-par round of 72 was switched to a 74, leaving her at 4-over for two rounds.
'There was a piece of moss right behind my ball,' Wie said. 'I knew I hit it but I didn't think it would result in a penalty of two strokes. I thought if you hit dirt it would be OK, but I guess I knew the rule wrong.'
A statement by the Ladies Golf Union said Wie broke rule 13-4 of the Rules of Golf, which prohibits touching the ground in a bunker prior to making a stroke.
'A stroke is the forward movement of the club, a backswing is not part of the stroke, hence a 2-stroke penalty was incurred,' the statement said.
It's not the first time in her short pro career that Wie has been penalized and found out about it later.
In her first pro tournament last October at the Samsung World Championship in Palm Desert, Calif., she took a penalty drop for an unplayable lie during her third round. At the end of the tournament, officials ruled she made her drop at the wrong place, should have taken a two-shot penalty and disqualified her for signing an incorrect card.