Usually a gracious competitor in defeat, McIlroy could not escape Pinehurst fast enough as he loaded up his car, got behind the wheel and left the property.
McIlroy was in prime position to end his barren run at the majors but shockingly missed two par putts inside of four feet over his last three holes and ultimately finished one stroke back of DeChambeau.
It marked the fourth runner-up finish in a major for the Northern Irishman including at last year's US Open, but none came in a more crushing fashion.
"He'll win multiple more major championships. There's no doubt," said DeChambeau. "I think that fire in him is going to continue to grow."
McIlroy began the day three shots back of 54-hole leader DeChambeau but, bolstered by a sizzling stretch around the turn where he had four birdies across five holes, had a two-shot lead with five holes to play.
The wheels started to come off when McIlroy bogeyed the par-three 15th where he failed to get up and down after his tee shot rolled off the back of the green.
He then made a second consecutive bogey when, for the first time all season, he missed a par putt from inside three feet.
McIlroy left the door open for DeChambeau when he missed the fairway at 18, advanced it just off the front of the green with his next shot, chipped it just past the hole and then watched his par putt from inside four feet lip out.
"For him to miss that putt, I'd never wish it on anybody. It just happened to play out that way," said DeChambeau.
The scene of McIlroy leaving Pinehurst was in stark contrast to last month's PGA Championship where runner-up DeChambeau went back to the 18th green to congratulate Xander Schauffele after a closing birdie sealed his win.
"At the end of the day we are all human," said Frenchman Matthieu Pavon, who finished fifth, three shots back of DeChambeau. "Rory has been chasing another major since many years. He is one of the best players in the world, a true champion. It shows you how tough it is.
"The more you want it, the tougher it gets, and the highest expectation you have for yourself, the tougher it gets, the more pressure you got into.
"Maybe this is a little bit of pressure that got him today for sure, but Rory is just a massive champion. I'm sure he will fight back and really soon."
