After the strange claims from Bob Weinstein that the events of Apollo 18 were real, the movie got pushed back to the graveyard of January 2012. Speculation leans toward the movie being double plus bad because of the move, but in truth, we’ll never know why the decision was made.
However, it doesn’t matter now, because according to Bloody Disgusting, the movie has been pushed up to the slightly more encouraging August 26th, 2011 release date it holds today.
So that explains why the trailer played in front of Scream 4. They weren’t just playing the 10-month-ahead-of-time hype game.