Where are the summaries from? I would say it's much more likely that a shadow library was scraped but if course that is also seemingly impossible to prove. One may be able to somewhat test that by asking for a summary of a book/text only available on a shadow library.
You could ingest all reviews that are extent in the online corpus, remove from the book all quotes found. Then ask the AI if a distinctive triples, say, of words appeared in their book, somehow, you'd probably need prompt engineering to get past "While I don't have access to the full text of the book [...]". A little maths and you might prove beyond reasonable doubt that the LLM was trained on the book.
Me: Has Sarah Silverman ever written about Boys' Market Manchester
ChatGPT
ChatGPT: As of my knowledge cutoff in September 2021, I do not have any information indicating that Sarah Silverman has written specifically about Boys' Market Manchester. Sarah Silverman is an American comedian, actress, and writer known for her stand-up comedy and her work in film and television. While she has written books and has often shared personal anecdotes in her comedy, I couldn't find any specific references to Boys' Market Manchester in relation to her work. However, please note that my information might not be up to date, as Sarah Silverman's career and activities may have evolved since then.
