Just a guess but perhaps it could be related to Hayate's brother? after all it was titled "Mystery room" so perhaps he stayed there for some time? When Athena first showed up she was looking for something Hayate's Brother had after all, so perhaps the room in question has a clue as to where it is
As a side note, that manager is freaken annoying T_T, feel zero sympathy for those tears; you don't control someones life like that, debts are debts and they need to be paid but things like "control her heart" and other crap she said makes her character unlikeable.