Ryan Garcia Partied Hard At L.A. Nightclub Hours Before Flunked Drug Test Revealed

Ryan Garcia clearly wasn't sweating his flunked drug test in the hours before it became known to the public ... 'cause TMZ Sports has obtained video of him partying hard at an L.A. hotspot on Tuesday night -- seemingly without a care in the world.

Garcia hit up Bootsy Bellows in West Hollywood at around midnight -- roughly 20 hours before it was revealed he had Ostarine in his system the day before his huge upset win over Devin Haney -- and he danced at his table with no signs of worry.

We're told by one person in attendance that Garcia appeared to be in great spirits the entire time he was there -- sippin' on tequila ... and even taking selfies with other clubgoers.

At one point, the DJ turned on a snippet of Garcia's new Haney diss track, "Haney Pack," which got the 25-year-old pugilist going even more.

Check out video from inside the spot ... you can see Garcia was shadowboxing as the tunes -- filled with jabs at Haney -- blared over the speakers.

Amid it all, Garcia found time to tweet about how much fun he was having ... writing on his X page, "Bootys lit."

Of course, it'd be hard to expect Garcia to act any differently ... as he said in a statement following reports of the positive test that he in no way cheated in the leadup to the big April 20 victory.

"Why didn't they come out with this before the fight?" Garcia said. "Why would they let me step into the ring as a cheater and come out with the victory and then post this?"