Well, you should be happy for him, if he is getting the help that he needs...
More than likely he needs to focus on himself and his own issues for a while. I miss my ex too, sadly he is still deeply in denial. It is hard missing someone, I know. Then I have heard other people say that once their addictive partner gets into recovery they end up changing so much, they don't even want to be in the same relationships with their former partners.
I'm sorry it's hurting. Have you thought about going to no contact? Might make things easier in the long run.