This whole "red zone" thing is highly questionable.
In one episode, they seem to be an island and never venture far from the town. In the next, they are shooting National Guardsmen after driving there and then walking to surround them or hunting Michonne in the woods. It is really spotty. They are aware of the prison but never investigated it. They had no idea that a guy was living in a cabin less than a mile from their walls but are immediately aware of a helicopter going down even though this may not have happened within sight of the town.
I love the show but this rubberband awareness of Woodbury is a bit frustrating.
They are aware of the prison. They talked about it, with the Governor even commenting that it's amazing there's a group in there, since Merle had previously scouted it and reported it "impossible" to clear.
Most people in Woodbury never leave town, but the scouts/henchmen do, when instructed and/or lead by the Gov.
Who's to say they didn't know of the guy in the cabin? They may have concluced he posed no threat and had nothing worth taking. Or they may have seen the boarded up cabin and chalked it up as sealed and abandoned.
Edited by head_creeps, 26 November 2012 - 04:53 PM.