Never seen that before on any flight but it doesn't surprise me, especially on UA.
I was supposed to be on that plane in 2L & 2K with my wife tonight. Thankfully as all of us know UA can't run an ontime operation and my flight is delayed over 2.5 hours because the inbound aircraft was missing crew. So glad I called GS when the flight took the delay and was offlined to DL in J, I would not have been happy had I read this and been on that plane one row behind the bedbugs.