I almost had one yesterday. After I start the boil my HLT becomes my chemical pot (e.g. I mix PBW into the hot water and start running the cleaning cycle). So, yesterday, while dead sober, went and grabbed the PBW, scooped out a tablespoon and walked right to the boil kettle.
Fortunately, my brain intercepted the signals to the hand and locked it long enough for me to go: "hmmm... that's probably wrong"