I just remembered I'd put a load of towels in the washing machine this morning, figured I'd toss them in the dryer overnight.
Opened the folding doors to the laundry space, saw the washer's lid was up and started taking out the towels and putting them in the dryer. My mind registered that the towels seemed wetter than usual after the spin-cycle-from-hell the machine inflicts upon them. Then I saw the Downy ball in the bottom of the washer and since I don't like leaving it in there, I reached in to grab it. Then I noticed it hadn't opened during the rinse cycle like it was supposed to.
Then it occurred to me. I didn't have to lift the washer lid to remove the towels, and the towels were much wetter than usual after the wash cycle.
The washer did its entire cycle, minus the spin at the end, because the lid was open.
I wasted a wash cycle, dammit!