uh oh!!! there's 13 sticky notes in total and once you get to the final three one of them will have a note that has a dialogue piece that says: "a key? what is this talking about? what screams: hades?" which is supposed to be a hint to look around the apartment. at this point, you'd recover a key from the pomegranate bowl in the kitchen and try to get to that secret door you can see in the hallway!