Definitely message him — try to hook the message onto a birthday, a holiday or some interesting reason that you were thinking of him — maybe you’re going to be in the same town as he is, or are taking a course that you heard he took — something like that, so it doesn’t seem like you’re desperate. I know you’re not — but I just want you to be able to give the appearance of interested, but chill at the same time. Having an excuse to talk to him about will help you with that.