Conspiracy theory?

A golf fan is believed to have unwittingly pocketed superstar Rory McIlroy’s lost ball in the final round of Sunday’s British Open, which could have cost him up to $203,000 in prize money.

McIlroy, 28, was penalized for losing his ball on the 15th hole after a wild shot, costing him a

slim chance of catching Jordan Spieth and the leaders. But a man was filmed apparently picking up a ball from shrubs.

McIlroy went on to finish in a tie for fourth, earning $477,000 in prize money. Without the twoshot penalty, he could have been third. He started the final round nine shots behind Spieth — and came within four of catching him — before the drama at Royal Birkdale.

The Sun, a British tabloid, posted a 90-second video that starts just after McIlroy had hooked his tee shot.

A fan who realized the golfer was striding toward him began filming on his cellphone. His footage shows another spectator — in shorts and holding a red umbrella — leaning toward thick grass. He then straightens up holding a ball and puts it in his pocket.

McIlroy strides into view and the hunt for his missing ball begins.

The man filming can be heard whispering to a pal: “That fella just found the golf ball!” He giggles as he adds: “He’s not told him! Terrible!”

The man thought to have taken McIlroy’s ball blended into the crowd and slipped away.

Eventually the player admitted defeat and declared the ball lost. He took a bogey 6 on the hole and finished the tournament 5-under par.

“There was great excitement because Rory was getting into gear and a magical comeback charge for title glory was on,” a fan who saw the incident said. “The mystery man’s actions have changed the course of sporting history.”