AW......I am sorry that this has happened and that you are blaming Yourself for it. I know that you were sooo hopeful for his lasting sobriety when he said that he was going to cut down on his drinking.
A relapse is sooo hard for the Partner......perhaps, even harder than for the alcoholic.....lol. The partner can put so much of themselves into the alcoholic, that it feels like when the alcohollic stumbles, that the Partner is the one who gets hurt, also.
Of course, if the alcoholic is not strenuously adhering to a program of recovery---like AA, and having the support of a sponsor and a counselor----it is almost invevitable that relapse is going to happen. Half measures won't work, you know.
From your last thread, I sure hope that you read "Co-Dependent No More".
And, reading the over 100 excellent articles in the "Classic Reading" section.
I hope that you found an alanon meeting----for yourself---as this is just too hard for you to go through alone.
Aw...I sure hope that you will put away the guilt (that you don't deserve) and your annoyance at yourself-----ad it is a misdirection of your own energy. AND----it amounts to your "enabling" him.
It is His responsibility to manage his sobriety---not yours! He knows the risky situations and he is responsible for making the decisions that protect him.
Surely, he was told in treatment that he needs to be very careful to avoid the people and places that are a trigger---especially, in early months of recovery .
I have been around lots of alcoholics, and I would bet my fortune that he drank more than that one bottle. It is not at all unusual for the alcoholic to be "sipping" before the Partner ever finds out.
Stop blaming yourself----he is just doing what alcoholics do. It is about him---not you.