You have to reach the milking room first. Then before you enter the scene where you help both Warren and Arthur. Luke(mc) will say that there's something he forgets. From there you can backtrack every rooms, go back to find that specific room.
Actually. My bad 😅. You need to progress another room, where you have to turn the lever. At the end, when you trying to exit the floor/fight the boss. Luke will say that he forget something. From there, you can backtrack to that specific room.
