KAVARNA, Bulgaria, May 18, 2013 (AFP) - The Belgian was beaten by Ryder Cup colleague Graeme McDowell 2 & 1 in the quarter-finals on the Thracian Cliffs course.
His challenge had unravelled on the par-four 10th hole when his tee shot flew into a public toilet close to the green.
He was then told that he had to take a one stroke penalty drop within the cubicle.
As it was impossible for Colsaerts to play from within the toilet, he was allowed to take a 'free' relief on his way to saving par.
"I'm sure now the whole episode at 10 is going to make all the TV news programmes, Facebook and all the social media sites with the caption: 'Here's some Belgian guy playing golf in some toilet block in Bulgaria'," laughed Colsaerts.
"It's the first time I've ever hit a ball into a toilet and you would have thought as a kid I would have been crazy enough to practice that shot (smiling) but I never did."
McDowell is the highest-ranked player in the event at number eight and had the toughest match of the three million euro competition earlier in the day in just managing to get the better of American Bo Van Pelt winning 1-up at the 18th in the last-16.
He will now play South African Braden Grace in Sunday's semi-final with the final to be played in the afternoon.
If successful, McDowell will become the first Irish-born player to win the event.
"This is an historic event and it's a trophy that has all the legends of the game appearing on it," he said.
"I think back to the golden years around Wentworth and watching all of my heroes winning this great, great tournament and I would dearly love to add my name to that list but there are three other guys still left in the event who also feel the same way as I do."
Grace had defeated Australia's Brett Rumford 4 & 3 in the morning and while he lost the second hole to England's Chris Wood in the afternoon, the four-time European Tour winner from last year levelled with a birdie at the eighth.
Their match was all-square at 14 before Grace sealed victory with birdies at 16 and 17.
"I can't remember the last time I played 36 holes in one day, but you know, it was a good day for me," said Grace.
"So far this week I've got off to a good start over the front nine, which has been the key for me."
Thailand's Thongchai Jaidee beat Sweden's Peter Hanson at the 21st extra hole on Saturday morning.
He then defeated Scotland's Scott Jamieson 4 & 3 after Jamieson had won through to the last eight with a 1-up victory over Chilean Felipe Aguilar.
"I am very happy with my two wins today and I am now looking forward to the semi-final and hopefully the final," said the Thai star.
"I only made one mistake today and that was on nine this afternoon, and the key for me is that I have been playing very solid and I am very happy with my golf game."
Thongchai will now play Thomas Aiken after the South African defeated Italy's Francesco Molinari 3 & 2.
Aiken had beaten Sweden's Carl Pettersson 6 & 4 in the morning.
Quarter-final results:
Branden Grace (RSA) bt Chris Wood (ENG) 2 & 1
Thomas Aiken (RSA) bt Francesco Molinari (ITA) 3 & 2
Thongchai Jaidee (THA) bt Scott Jamieson (SCO) 4 & 3
Graeme McDowell (NIR) bt Nicolas Colsaerts (BEL) 2 & 1.
Semi-finals on Sunday:
Thomas Aiken v Thongchai Jaidee
Branden Grace v Graeme McDowell