From a share of second behind eventual champion Scottie Scheffler late in his final round at Quail Hollow, Scott leaked four shots in his last five holes to tumble into a tie for 19th with fellow Australian Cam Davis.
Scott closed with a Sunday 73 to finish the season's second major in Charlotte at two under par, nine shots behind Scheffler after pulling to within four of the world No.1 through 13 holes.
While notching a 35th top-20 finish at a major, and a milestone 50th top-30 result, the former world No.1's watery double bogey at the last could have huge ramifications.
A top-15 finish would have earned Scott an automatic exemption into the 2026 PGA Championship in Pennsylvania.
This week's tournament in North Carolina was the 44-year-old's 95th consecutive appearance at a major, the longest sequence among active players.
To put his remarkable longevity in perspective, Scott's unbroken 24-year sequence stretching back to the 2001 British Open is almost double that of the next-longest run among active players - Jordan Spieth's 49.
Tiger Woods' record is 46 in a row, while Scott's streak is second only to Jack Nicklaus's 146 without missing a major between 1962 and 1998.
Exempt for this year's remaining two majors, next month's US Open at Oakmost Country Club and the British Open at Royal Portrush in July, Scott will extend his streak to 97, then 98 when the 2013 Masters champion returns to Augusta National in April.
But now the world No.39 must earn his place in next year's PGA Championship field.
The quickest way would be to win a 15th PGA Tour event, while holding down a top-70 position in the season-long FedExCup rankings would also guarantee a start to edge his run to 99 straight major appearances.
More immediately, Scott will lament his late collapse.
Perhaps inspired by his great mate and fellow 44-year-old Justin Rose's runner-up finish at the Masters, Scott was on track for his own second-place showing at the same age until he reached the short par-4 14th hole.
He had birdied the hole the three previous days but this time skewed his tee shot into the rough and was unable to get up and down from a greenside bunker to save par.
Scott dropped another shot after missing the green on the notorious 216-yard par-3 17th before racking up a dreaded double at the last, ranked the second toughest at Quail Hollow.
With a fifth birdie of the day at the 15th hole, Davis briefly jumped into the top 10 at five under.
But he too finished poorly with three successive bogeys to settle for a third top-20 finish of his major championship career, after sharing fourth at the 2023 PGA Championship and tying for 12th at last year's Masters.
Elvis Smylie, the only other Australian to make the halfway cut, closed with a 74 to share 72nd spot at 10 over on his US major championship debut.
Jason Day, Cameron Smith, Min Woo Lee and Karl Vilips all had the weekend off.
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