What Anvilhead said, and this:
I haven't said anything to him about going to AA or give him any treatment plan suggestions. I just made my decision and walked. I wouldn't do that to a friend, but I did it to him last night....and I feel really bad about it.
You don't have to, it's not YOUR problem.
He knows about AA, he knows he can look in the phone book, talk to his friends, his doctor, his religious leader, go to a book store, or library, that there are many options, if he chooses. He's a grown man who can figure this out on his own.
You have not sold him short. You have nothing to feel bad about, except maybe a temporary, short term mourning over what may have been and is not, and will probably never be (and in truth, probably never was).