Charlie Sheen's Porn Star Extortion Lawsuit: It Ain't Over 'til it's Over

Charlie Sheen has dropped his extortion lawsuit against the porn star who locked herself in a bathroom during his Plaza hotel meltdown last year -- but we're told ... it's only because the chick is M.I.A.

Sources on Charlie's legal team tell TMZ, it's true ... they pulled the plug on the lawsuit against Capri Anderson -- in which Charlie accused her of trying to extort him for $1 million -- but they did it "without prejudice" ... which means they can re-file the same suit whenever they want.

Charlie hasn't given up the fight -- according to sources, the only reason he dropped the suit was because he couldn't track Capri down to serve her with papers ... porn stars are slippery.

But if Charlie's people find her ... we're told the lawsuit could be back in play.