Help me tweak my story plot? i need some constructive critism. (:?

I like the basic premise, but there are some serious problems that I don't know how you could work them out plausibly. First, for someone to play that kind of "joke" on their mother would be hideous. A missing teen means police involvement. If there is evidence pointing to murder, there would be Amber Alerts, townspeople searching, etc. The detectives would go through her room looking for any clues to who took her, including reading diaries. It would be very hard for even the mother to forgive her for such emotional agony and the friend would never trust her again. If that is what you are going for, then it could all be worked out. However, if she had previously been someone who did cruel pranks then why would your character have even stayed friends with her for so long? Just some points for you to think about. In the meantime, I like the answer where the main character is led to the place where she committed suicide but maybe the boy isn't asked to clean out her room. Maybe the mom finds something in the room (a book that was special to the both of them?) that she gives him and he discovers the clues in it or he re-reads it and the name of a place in it that they used to talk about triggers an idea of where her body is?