There would still be potassium in there, unless it’s pulled out by the frying oil.
Elements can’t get lost in a chemical reaction. You can only change the molecule they’re part of, so it might not be processable by the human body, but the potassium isn’t going to disappear.
> Why would something being an element mean that heating it as part of a food wouldn’t act as a catalyst for some chemical interaction?
It sounds like the person thinks that chemical reactions can make elements change/disappear, which is not the case. And I specifically mentioned the Oil removing the potassium as an option.
Elements can’t get lost in a chemical reaction. You can only change the molecule they’re part of, so it might not be processable by the human body, but the potassium isn’t going to disappear.