The Northern Irishman was initially ribbed about the incident when it was brought up as he spoke to the media ahead of his appearance in this week’s Hero World Challenge in the Bahamas.
Replying to someone saying ‘nice shirt, it’s in one piece’, he replied: “It is. It's another joke you tried to make that's not that funny.”
When it was mentioned again, he explained what had happened, saying: “I pulled on my collar and it ripped. I don't know if I've ever done it before.”
Asked what had happened to the ripped shirt, he said: “I went to the pro shop, bought a new one, threw that one in the trash.”
McIlroy had been on course to land another victory on the Earth Course at Jumeirah Golf Estates until he suffered an unlucky break when his second shot at the 15th hit the flag and ended up in a bunker.
That led to a disappointing final four holes as victory went instead to Collin Morikawa as he became the first American to win the Race to Dubai.
“What I was angry about was how I reacted to the bad break, not the bad break or the fact I didn't win the golf tournament, because Collin played great.,” said McIlroy
“And even if I hadn't had that bad break, there was no telling that I was going to win the golf tournament.
“It was just my reaction to that bad break that made me angry because I basically lost my head after that and made a bogey on 16.
“So it was more just angry at the fact of how I responded to that was my big thing. The fact that I didn't win the tournament was totally fine, but it was more just the reaction of what happened after the break on 15.”
McIlroy is making his first appearance in the Hero World Challenge hosted by Tiger Woods since 2014.