Well, let us remember that soon after Montag's televised "death" the entire city gets blown to smithereens, so I am not too sure that they would be in any fit state to worry about Montag's escape after all. However, let us just assume for one moment that in a different parallel future for the city Montag's escape is discovered. To be honest, I don't think for one moment that this would happen. This is because the grip of power that the state has over its people and the media is so complete that they would never allow anything to be broadcast that would contradict the "truth" that they have already transmitted.
Let us just also focus on the kind of people that make up this city. The main people we have met in this novel are Mildred and her friends. They are shown to have been so conditioned by the media and state control that they would never think of contradicting the media for one second. They would believe so totally the news of Montag's "death" that they would disbelieve anything that might suggest otherwise. Therefore, even if news of Montag's faked death did get out, which it wouldn't, it would have no impact whatsoever.