I agree, go see him if you can. Or email him, and leave an open invitation. Cos he may not be able to respond for who knows how long. He will have his own battle with the news, and need time to process, or he may not even know what to say... I'm thinking something along the lines of 'dear dad, I really miss you, but I left bcoz... I would really like it if we could rebuild our relationship, feel free to respond whenever you are ready'... That way,you dont feel instant rejection if he doesnt reply instantly.