when is it an appeal?

[jmkupka]

"An example of a live-ball appeal not needing a verbal: Play at the plate - runner misses the plate, F2 misses the tag."

Even in this case, we want to be sure of the appeal. If F2 slaps the ball/glove on the plate & holds it up to me, common sense will interpret that as "I missed tagging her, here's my appeal". If she stands up and happens to step on the corner of HP while throwing back to F1, nothing.