Goodness, that's an easy fix. Don't panic.
It could be as simple as some thin superglue, then pressing the hard plastic backing onto a perfectly flat surface, like a piece of waxed paper and a glass table. Hold it down flat for 5 minutes.
If there are some holes visible from the sides, and you're super fussy, fill those with some epoxy filled with black phenolic plastic (or acriglas, which is the same thing) or epoxy and black pigment...like the scrapings from a watercolor set. It's not structural.
It'll probably only last you another hundred years, and then you can have a new pad ground.