This picture is from a friend whose flight left Arcata/Eureka Airport (ACV) this morning. The foot warmers had been removed from the suitcase, and this note was left. I checked the TSA website, and there seems to be nothing prohibited about these items, even when you consider looser definitions of some of the prohibited items. Upon further research provided in post #4, it would seem these were incorrectly removed.

On a side note, I also like the paragraph about lighters being prohibited in carry-on luggage. It would be something one could test at ACV considering one lighter is now allowed. I'm sure the TSOs at ACV, however, will insist that the website is out of date, even if they provide the URL as they did on that sheet.