Since we don't know what was actually purchased and what was actually destroyed, how do you expect us to furnish an example? This would require the destroyers to admit it, and beyond that it would require all of them to admit it since more than one of them might have been responsible for the extinction of one text. Seeing as they were already keeping this operation under wraps, I don't see that happening. "possibly extinct because no copies available online" is probably the best we can do.
The distributed nature of the problem and the utter lack of transparency are huge factors here too.
These companies are buying from small book stores; surely these collector types would know if they lost any one-of-a-kinds? Or at least someone would be keeping track of extremely rare books disappearing (especially now since this matter has been public for weeks).
Regardless I feel like they gotta figure this out for optics reasons. “So and so books are lost forever to Anthropic’s servers” is much more outrageous than “Anthropic is destroying a bunch of books that have other copies” imo.