Hi Corkie, Welcome to SR!
I read your story and it reminded me of a situation I had with my AH. He was on a court ordered at-home sobrietor that he had to blow into 3 times a day. Well, one day the alarm kept going off ~ he'd redo the test and the alarm would go off again. Finally, he called the company and they told him that the test was showing up as positive.
"How could that possibly be?!"
"There's something wrong with the equipment!"
"Maybe it was something I ate!"
"Do I really think it's possible he would risk things by drinking?!"
Well, he kept up that line of bs (with me believing him) right up until the police showed up to arrest him. It seemed totally out of the realm of possibility that he would risk his freedom for a beer. Later he admitted to me that he'd been drinking. He just figured he could get away with it. I will never again underestimate the power of the drink. Trust your instincts!