The incident occurred at a crucial moment of the world number 34’s World Championship qualifying victory.
The 16 seeds will be paired with 16 qualifiers as the delayed 2020 World Snooker Championship finally nears its start.
It was the fifth time in the last ten years that O’Brien had participated in a deciding frame in the final qualifying round.
The Scot has proven to be a master at World Championship qualifying in the past.
The Irishman was attempting to qualify for the World Snooker Championship for the first time in six years.
Between the pair, they have lost eight times in the final of the World Snooker Championship.
The Irishman is fighting to maintain his place on the Main Tour after 30 years as a professional.
The 58 year-old hasn’t qualified for the main stages of a World Championship since 2006.
Cahill stunned Ronnie O’Sullivan in the 2019 World Championship after becoming the first amateur to qualify for the main draw.