ah, it sounds like you are really feeling sad about this guy. not getting closure is difficult, is it that you didn't give him closure or that he didn't give you closure? I'm a just wondering whether you are able to talk to him if it was you who didn't give closure, or is there a way you can give an apology and explain things if you didn't give closure, or is it that he wasn't or couldn't speak to you about why things fell apart.
when you spoke to him 5 months ago was everything ok? or was it awkward a bit?
do you have his details to write to him or get a message to him or anything. I think you have to get your feelings to him because only he can give you closure, but it doesn't sound like you want closure, its sounds like you want to get back with him! nothing wrong with that, but; I don't think you can realistically do anything until you talk to him or write to him and see what he feels about you and this situation.
if you find out he's not into you then you will have a bit more closure, but if he still likes you you might be able to meet up.
but talking online to everyone but him cannot give you the real answers in this situation, you have to find the courage to talk to this guy.
maybe he feels down too because he hasn't got closure or he would like to talk to you.
maybe things he does reminds him of you too?
not having closure may be you realising he means a lot to you. so you are getting emotional. if this man has done nothing wrong, then not having spoken to him for so long may be really hard for him too!!!!!
do you know if he is single? do you know if he likes you still? did you go out together or was it just you wanted each other?
what makes you sure you cant be with him, can you talk to him,
he may be able to think of ways that you hadn't thought of that you can be together, if he likes you and wants to be with you. but you wont find that out unless you talk to him!
IF you are serious about sorting this out you are going to have to talk to him. unless you are prepared to do that I think you are never going to going to get over this. and will date other guys not really wanting them. if this guy is perfect for you you can find a way.