What are Joseph's ideas for an escape in The Silver Sword by Ian Serraillier?

The protagonist of The Silver Sword, Joseph, is a school teacher. He is imprisoned in Zakyna, a Nazi prison camp in the mountains of south Poland for the crime of turning a picture of Hitler in his classroom to face the wall. He considers cutting the wire fence that surrounds the camp but eventually decides this is impossible.
Instead, he starts a fight with a guard in order to get himself placed in solitary confinement. From there, he ambushes a guard delivering him food with a slingshot he made, puts on the guard's uniform, and escapes. During his 18 months at the camp, he memorized enough about the guards' movements and common hangouts to convincingly play the part. At one point, when questioned about where he's going, he names his destination as Shangri-la, a bar the guards frequent.