You were talking to professor Fig and he said he found a map to a key for what you were looking for. It was in the restricted section of the library.. the only person that knew how to get in there was your dear friend Sebastian Sallow. The bad thing was you were a Griffindor and he was A Slytherin. So if his house saw him sneaking around with a Griffindor you both were screwed. So it had to be secret