Inspecting the door does show that the chain is unlocked, of course, but also that there has been tape used to ensure that any breaking of the chain would have been impossible. Residue on the door shows that there had been tape sealing the outside of it, as well.

Interacting with these things... show that this was just one layer of the torment.

The rest was just as bad, if not worse. Remember that one time Battler said he didn't want to go into it? Remember that?