Flower, while he was there, he picked up some tools that may be useful to him even now. Words someone said, special thoughts to remove cravings, a list of meetings...he has not come away empty handed. How he chooses to use those tools remains to be seen, but having tasted sobriety I think he may want to try again some time soon.
That said, if you paid for this rehab, maybe next time he could try The Salvation Army program, it's free and a very good program. Any program is about as good as the resident's willingness to work it.
My heart and prayers go out for you and for him. I know the sinking disappointment you must be feeling.
Hugs from my heart to yours.