It's heartbreaking- I did a lecture on drugs for a course in my university and after researching it I found that unfortunately you are right - one can't really get rid of the drug craving - a user will always have structures in his brain that changed in a way he will always want it. Even if he manages to withdraw, some event - the sight of the drug, a smell, a situation - can ignite it back fiercely.
I am really sorry for your friend and I can understand how it hurts you even though you did not speak for a year. I have friends close to my heart that I didn't speak to for a year or so but if we meet it will be like we never separated. It is that kind of friendship.
Thanks for sharing, I send you my condolences.