This update makes me so happy.
Years ago, we had a catsitter go through an entire $1000 bottle of scotch DH had been given as a work bonus. This was not someone staying with us but a neighbor popping in; we realized he'd consumed the scotch after we'd stopped speaking to said neighbor for various unrelated reasons. It was pretty heartbreaking.
Your situation, however, is not heartbreaking. These are good people.
My question, though: did they realize the Opus One was exceptional while drinking it? Or did they have a come-to-Jesus moment when they googled what they'd consumed?