If you don't know the books position under the foil, and the hole is just big enougn to show it's waldo, you cannot get the coordinates, but you know that the person who covered the book with a punctured foil knows where waldo is.
People use the similar concept in geocaching when they forget to bring a pen... take a photo of a geocache against a neutral background (asphalt, grass,...) thus proving they found it, but not revealing/spoiling the location to other geocachers.
But if you don't know the position of the foil, what does it prove? The other person could just move the foil around arbitrarily until it randomly fits.
Imagine having a where's waldo book, looking for waldo with a friend, and your friend says he's found him... you don't believe him, but he won't show it to you, because then you'll know the location of waldo too. How can he prove, that he found it, without showing the location to you? By taking this punctured-foil approach, he can prove it to you, that he actually did find it, and do it in a way, where you know he really found it, but you still don't know where it is.
Moving the foil randomly enough might work with a book, but this is just an example of a mathematical principle. An rsa key might be between 1 and 2^4096, randomly guessing the number is practically impossible (atleast with current computing power and without waiting literally millions of years). But if the owner uses the key and signs a number you gave him, you verify the signature with his public key, you know that he actually has the private key, but you dont know the actual key.
Well whoever's doing the verifying would need to have a way to align that piece of foil in a way that shows the position, and unless both people know that process it's useless anyway.
If there's infinite possible alignments then you've given no data, but a piece of foil with a random hole in it. Like giving you two random numbers and you coming up with a function that maps them to waldo's position.
You might not have understood how this works. The prover shows the fact that they know Waldo's position by showing the page covered in foil to the verifier in person (or by taking a picture). The verifier does not manipulate anything.
Obviously, there's no way to verify that the page under the foil is the page you think it is. This is more of an analogy / tool to explain things vs an actual secure protocol.
