After being rescued, he will wait in the room with the blue door. When Ronald Shiner complains about the lack of food, he rallies up the other survivors in the same room, including Nathan, to head out and look for food.
If Frank does not stop Ronald's mutiny, Nathan will leave the Security Room along with the other survivors in the same room. They will no longer count towards the number of rescued survivors.
During the cutscene in A Strange Group, Nathan is shown seated in the same row as Ray or at least close to the other survivors, but during actual gameplay, he is in the back of the theater, on a separate seating platform.