Her Secret, the Billionaire's Heir

Katie has a secret that she has been trying to desperately keep for years. However, on the last night before is to leave for a prestigious internship, she spills her secret to Mike thinking that he is too drunk and won’t remember it. Without a word, she leaves the next day and she hasn’t returned since. That was six years ago.
Mike also has a secret. He wasn’t drunk that night and was just acting. He had been acting drunk for years when the group would go out drinking together because he found Katie would talk more freely to him then. He was so excited when she finally revealed her truth. However, Katie left without saying anything to him and he hasn’t talk to her since. Mike, however, won’t give up on her and has been searching for her ever since. He won’t stop until he has found his Katie.
Will Mike ever find her? Does Katie have more secrets? What is the real reason that she doesn’t come back to home?