Thailand's Thepchaiya Un-Nooh fluffed a maximum 147 break by missing the final black - and said he did not know he had squandered £44,000.
Un-Nooh had been set for the cash prize in the sixth frame of his third-round tie with 2013 champion Neil Robertson at the UK Championship in York.
But the 30-year-old world number 36 said: "£44,000? I wish you'd told me before the black.
"There was too much pressure," said Un-Nooh, who was knocked out 6-2.
"I am so disappointed. I have never done a 147 in a big tournament like this before."
Australian world number three Robertson said he was "absolutely gutted" for his opponent.
"Poor Thepchaiya," he said. "That prize would have meant a lot to him.
"But I am delighted to win. I was 3-1 up and should have been 3-1 down. I am feeling really good.
"My game is definitely there and now I need to put it together at the business end of the tournament."