Never one to miss a media opportunity, Trump, the owner of the Blue Monster course in Florida, got a scuba diver to retrieve the 3-iron club which world No. 1 McIlroy had thought he had seen the last of during Friday's second round at the WGC-Cadillac Championship.
The 68-year-old American entrepreneur presented it to McIlroy before his final round Sunday, telling him that it was unlucky to continue playing with 13 clubs as against the usual 14 allowed under golf's rules.
"He's never one to miss an opportunity," McIlroy told the official PGA Tour website after his round. "It was fine. It was good fun."
Not that opportunity knocked for McIlroy when he chose the 3-iron to play his third shot to the 18th and final hole of the tournament and promptly found the water again.
The Northern Irishman feigned to repeat his earlier antics, before placing it back in the bag.
His mistake led to a double bogey six and left him tied for ninth at one-under-par, eight shots behind winner Dustin Johnson.
McIlroy had promised to return the club to Trump after the round and was as good as his word.
"We're thinking about auctioning it for charity or doing a trophy case for Doral, putting it on a beautiful mount," Trump said.
Johnson is looking set to be one of McIlroy's main rivals in the first major of the season, the U.S. Masters at Augusta, next month and his victory completed a triumphant comeback to the PGA Tour.
The 30-year-old American took a six-month break from the Tour last July to cope with "personal problems" and returned earlier this year.
Johnson finished with a three-under 69 in testing conditions to leave him one ahead of long-time leader JB Holmes and two clear of Bubba Watson, the reigning Masters champion.
Johnson celebrated on the 18th with his fiancee Paulina Gretzky, the daughter of ice hockey legend Wayne, and their newly-born son.