The world No 14 had to play in pain for two days during last month’s WGC-HSBC Champions in China after claiming he had slammed his right hand in his hotel room door.
But he now admits he has “no idea” what really happened and reckons he did the damage during a sleep-walking episode.
McDowell told the Golf Channel yesterday: “I woke up out of this dream and I was standing next to my hotel room door with the door open, in my boxer shorts and three seconds later I had the most searing pain coming through my right hand.
“I have no idea what I did to it.
“Now if my caddie had turned up the next morning and told me that story, I wouldn’t have believed him. But he watched me go to bed at 9 o’clock that night for an early night.
“That was my first sleepwalking experience and believe me it wasn’t a good one for me. I have no clue what happened.”
McDowell had to play with a baseball grip for the next two days and eventually finished tied for 42nd at Mission Hills.
He went on to play in the Australian Masters and the DP World Tour Championship in Dubai before ending his two-year victory drought at Tiger Woods’s World Challenge in California just over a week ago.
Meanwhile, McDowell believes Tom Watson would be an “intimidating” US Ryder Cup skipper in Scotland in 2014.
The American legend, 63, confessed in Australia at the weekend that he would be delighted to take the job if he was offered it — 21 years after leading the US to their last win on European turf in 1993.
Asked about the chances of a Watson captaincy at Gleneagles, McDowell said: “It’s an easy question to answer when Tom Watson throws his hat in the ring. Traditionally the PGA of America picks a player between the ages of 40 and 50, typically a former US PGA champion.
“I’d say they will change that ‘rule’ if Tom Watson threw his hat in the ring. He’d be a pretty intimidating captain for a European player.”
Larry Mize and David Toms are also being mentioned as potential US skippers in 2014.
But McDowell has no doubt that Paul McGinley faces a now-or-never scenario in the race for the European captaincy.
McGinley is locked in a grim battle for votes from the Players’ Committee with former stable-mate Darren Clarke, with a decision expected in Abu Dhabi in January
“Paul has stated his case the last four or five years, he’s captained the Seve Trophy side a few times. He did a nice job,” McDowell said.
“He’s got a lot of great qualities — leadership, organisational, strategic. He could be a great captain but if he doesn’t get it next time round, he’s probably never going to get it.
“Darren Clarke certainly will take it next time and if he didn’t take it next time he’d take it the time after that.”