Also spotted at Home Depot yesterday

Several boxes (not a vast amount, but enough to notice on the way past) of diesel exhaust fluid.  Arbitrarily blue-colored, if that matters.

So, it's not all gone; the locals haven't been snapping up all they can find.

I didn't take note of the price, but then I don't know what the stuff is supposed to cost anyway (see: tractor small enough not to need it).