Oh no! Your pad fell out and it's nowhere to be found. Here's a quick fix for that if you're in a pinch.
You need Silly Putty and "Saran wrap" style food wrap.
Push some Silly Putty into the pad cup, wrap the food wrap around the pad cup, then gently press down on the cup so that the putty conforms to the tone hole and makes a seal.
That is all.