The incident occurred on the final possession of the Hawks' 118-117 loss to the Dallas Mavericks on Wednesday at American Airlines Center.
Young had been knocked to the floor while setting a screen on Dallas center Willie Cauley-Stein before the inbounds pass with 4.7 seconds remaining, preventing him from getting the ball as the play was designed.
After Danilo Gallinari's difficult buzzer-beater attempt clanked off the rim, Young ripped out his mouthpiece and stomped toward referee Josh Tiven to protest the critical no-call.
Tiven, the crew chief, told a pool reporter after the game that the contact from Cauley-Stein was "deemed incidental," so he didn't blow his whistle. Tiven said that the officiating crew came to the same conclusion after reviewing video of the play postgame.
The NBA said Thursday that "the play that Young disputed was correctly ruled a no-call."
"Under the playing rules, Dallas' Willie Cauley-Stein was entitled to a normal step on a screen from behind, which he took, and which led to incidental and legal contact between Cauley-Stein and Young," the league said.
Young had 25 points and 15 assists in the loss.
"I'm not going to run away from the ball with four seconds left and we're trying to win the game," he said. "I'm not going to fall just to fall at the end. That's just the most frustrating part. Not really having an opportunity to make a play at the end is just really frustrating."