Hey, anyone else catch that the Gov even knew about their trip to see Morgan? How the hell did he know that? Didn't think even Andrea knew that. He also knew what they brought back.
That means the Gov knows about Morgan - which means Morgan is a threat - which means Morgan will be in this battle somewhere. Count on it.
Yeah, they must be watching the prison.
The governors lackey dude told Hershel he "recorded" the battle (attack on the prison) for future history.
They could have video cameras set up in the woods monitoring the prison.