At any rate you can force the infringer to disclose what works they use as input.
Copyright law doesn't encompass novel uses, but courts can and will deal with it.
That's a little bit like "If a tree falls in the forest but nobody hears it..."
I mean, sure, "theoretically" any number of things can be infringement. But it's obviously a gray area, so it only really matters when somebody brings a suit and a work is found to be legally infringing.
Some cases are pretty obvious, but even literal copying isn’t always copyright infringement (e.g., if the material is arguably not eligible for copyright protection).