the diary
She, (Shue) picks up a lil notebook to write down a number but notices handwritting. so it's a diary, alright, but who wrote it? and when?
coolness
I think she wrote in it and doesn't remember. Upon thinking about it, I also think it was her diary all along and that she doesn't remember hiding it.
My problem with that scene is that the lady on the phone says that NYU doesn't have any record of Jenny. If Jenny wasn't supposed to be important, why not have the lady start rattling off a phone number while Laura noticed the writing and started freaking out or simply state that it is against university policy to give out personal information on students. If it was a red herring, it was a bad red herring.