It's almost like no one cares that Conor McGregor LOST to Floyd Mayweather -- at least judging by new video of the UFC star partying in Spain. 

Conor got the VIP treatment at the Ocean Club in Ibiza -- where he was turning up with his girlfriend/baby mama Dee Devlin after a friend's wedding. 

Props to Conor for shaking hands with everyone who approached him -- couldn't have been a nicer guy to all his fans ... even the dude wearing an old-school Pau Gasol throwback Lakers jersey. 

Yeah, they still have those! 

Meanwhile Floyd's still in Vegas where he hit a $100,000 jackpot on a video poker machine Monday night ... 'cause he really needs more money.