Similar to trace amounts of blood invisible to the naked eye, that is not how mold works. We could not have kept the potato.

[He's not going to explain mold, though, not while he has to deal with this gross cut and grosser bandage. That, he gingerly peels the rest of the way off and tosses out, ew. This time he doesn't yank Leon's arm around in a panic, so his rudimentary first aid is actually quite gentle! Appreciate him.]