well that sucks. but, honestly you can't force people to change. If he doesn't want to, you gotta let him do his thing

Did he offer you a beer to announce his regression?

You did your best. is correct. You can't do all the work for him. If he ultimately doesn't want to be sober, it won't happen.

..at least he said "Thanks"

Sorry to hear that man. You did what you could but at the end of the day you know its each persons choice.