The 42-year-old missed out on the chance of claiming a second ranking title, fresh on the back of triumphing at the Northern Ireland Open last week, in rather bizarre circumstances at the York Barbican.
King trailed his fellow Englishman 3-1 at the interval when he took his cue to the tournament office to rectify an issue with a sponsor logo, but the Romford-born potter failed to bring it back to the arena and was therefore docked a frame.
"It's just one for the silly book," he told BBC Sport. "I have now done two things in three days that I have never done in the rest of my career - winning a ranking tournament and forgetting my cue.
"I was in a daze, had my cup of tea, had my banana and left my cue in there. Then I came out to the arena and thought 'oh my god, where's my cue'!
"If I'd said to Sam 'can I borrow your cue to break off' and then said I was going to the toilet, I wonder if I wouldn't have been punished?"
The 4-1 deficit would eventually end with King falling to a shock 6-2 loss, but he did rack up a 141 during the match and is now in contention to collect the £5,000 prize for the tournament's highest break.