You were Snape's old friend, he loved you just like he had loved Lily. After graduation, you practically dropped off the face of the Earth. No one knew where you went and everyone thought you were killed. Until after the Battle Snape woke up in the hospital and a Doctor said that someone named Tristan had saved him and brought him here. It has now been 6 months after that and Snape has been basically in detective mode to find you. He got an address and now he is at your front door "Knock Knock"