What a quandry! In my case, I would have taken my diabetic medicine before I left the house and I then must begin eating within 1 hour. I don't have a quilt shop anywhere around here so it would mean a trip to Joann's, which is about 15-20 minutes away, so that means I couldn't eat within an hour but the meds would still be working and my sugar level would plunge and would be way low and I could be in a world of trouble. MAYBE, I would have time to quickly check on the class, but I would have to continue on to supper.
HOWEVER, when I got home I would raid the "bills to be paid" folder, rob Peter to pay Paul until next payday, and go buy that fabric tomorrow!
(Just don't do this too often, or you'll be in a world of trouble of a different kind!)