TMZ Sports has learned ... the ex-Bucs wideout watched his old squad lose to the Rams in Tampa -- and then he made his way down to Miami to celebrate.

We're told the 33-year-old hit XXIII Club ... and copped around $15,000-worth of bottles while there!!

Brown rocked a huge fur coat ... and was the life of the party at the packed venue -- which, at one point, played his new "Pit Not The Palace" song for the crowd.

Of course, Brown was in great spirits ... because, after all, the team that he says screwed him over earlier this month finally fell in heartbreaking fashion to L.A. earlier on Sunday.

In fact, Brown was so pleased with the result on the field, he trolled Tampa Bay on his social media page with an edited "Bucs eliminated" meme, and later tweeted that Arians was a "barbarian."

It seemed Brown had been moving on from his beef with the Bucs -- remember, he told us recently he and Tom Brady had hashed things out, and said just before that that his shirtless exit from the team was not very professional.