Reggie Bush hit an L.A. hotspot last night ... partying like he just won the Super Bowl -- problem is, his winless Miami Dolphins JUST had their asses handed to them by the San Diego Chargers.

Bush was spotted at XIV in Hollywood around 10PM last night -- gripping a Corona while go-go dancers in body paint danced their faces off and people wearing glowsticks ... did whatever it is that people wearing glowsticks do.

Roughly six hours before the party, Bush wrapped up another lackluster performance on the field ... rushing for a mere 50 yards during a 26-16 loss in San Diego.

For the record, Bush is a grown-ass man and can do whatever the hell he wants in his downtime -- but it's a questionable move for a guy who's been HEAVILY criticized for playing like crap this season.

TMZ placed multiple calls to Reggie's agent for comment -- so far, no response.