Board Thread:WARNING ALL USERS False Info\Spoilers/@comment-13059881-20130730034947

When stiles is talking to his dad and trying to tell him about werewolves being real, he says that the Darach was clawed up and left in the woods. Then Cora added "that's what we think" and stiles confirmed that its what they think. Then his dad asks for the file at the hospital. So I'm wondering how stiles knew about the Darach being slashed? 