The rat scuttled on the side, ignored by many in the barracks, the place which was used to hold traitors in custody if they were found. Hence for the same reason, there were only two cells in this place and the security was not as tight, inside.
Adam even had a freedom to move around his floor and the bars could be easily opened with a single push.
Not to mention, the soldiers that were on guard duty inside were playing cards showing that they didn't give him thought to their job. Of course, they still have to provide Adam with any kind of entertainment and food if he asks for it, but there is always a limit.
Making it appear that this place was not a prison to Adam, and if he was the kind of person he makes others think he is, he would have fallen for their act.
But he knows, out of this floor, the security of this building was tight and there were even some curse users in hiding, brought over after the Sleep incident that shook the barracks.
