My man just fell off the wagon?

so my bf stopped drinking a year ago bc he admittedly had a problem. he's been the happiest i've ever seen since then...then after work today he called to say he had a bad day at work and he needed to calm down and at first said he wouldn't talk to me again tonight and then before he hung up said he would call later. we usually say goodnight around 9 so at 10:30 i was starting to get irritated. then he finally calls and says he's at a bar drinking and he's pretty buzzed. do i have the right to be pissed about that? he hasn't had a drink in over a year. while this is his decision at age 35...this could effect our relationship if he starts drinking again...what do you think? do i say something or not? i know he'll regret it...do i just let him realize this was a stupid decision?