Let's see, how to break this down:
1) Manhunt 2 on PC is rated Adult Only, as they didn't cut out some of the content that made it Mature on consoles
2) Since the game was rated AO and the United States is perpetually embarrassed by itself, no retail store would carry it
3) Direct2Drive was the only digital distributor willing to carry AO-rated games
4) Direct2Drive was just purchased by GameFly, whom are just as embarrassed as most retail chains, it seems.
5) GameFly has removed Manhunt 2 from D2D, making it basically impossible to find outside of pawn shops, mom-and-pop game stores, or via piracy…I imagine. I wouldn't know anything about that, of course.
This whole thing was apparently totally unknown to Rockstar until a determined fan inquired about it, and they were so grateful he brought it up that they sent the guy a free copy of the game and a bunch of swag, to boot. Now that's customer service!
Thanks, RockstarWatch!