Welcome to SR!!
I, too, am a recovering addict, as well as a recovering codie (codependent). Unfortunately, relapse is always a possibility with A's (addicts). However, the stronger our recovery is, the less it is a likelihood.
I hope that you realize it is no fault of your own that you didn't see this relapse. Many A's are quite capable of hiding their using...up to a point. It sounds like he realized he needed to quit before he got in too deep.
I agree with finding your own support. I don't go to meetings, although I know they help many addicts. I do, however, have the support of many recovering addicts (here), and others (f2f). I truly don't know what I would do without the support I have gotten, both for my addiction and my codependence.
Hugs and prayers!
Amy