I wish I were like you, I wish I could KNOW when he's been drinking but I still cannot tell, and I think that he has had some dry drunk episodes that look so much like he's been drinking.
I spent a lot of time thinking, "Is he? Is he? Is he?" Like, months. That was a good sign he was white-knuckling it or riding the pink cloud. And also a sign that I wasn't focusing on myself enough and giving him my sanity and well-being.
The difference was when I knew he'd made the jump to drink again. Some of the best advice I received on this board was not to follow him around in fear, but to let go and know that the truth would reveal itself. Surely enough, he can only hide it so long. Eventually he gets sloppy and thinks he's got me in the bag. C'est la vie.