How do you know, how the model works? If there was an index of all Micken's writings, or even if the model searched the web before feeding the response to you, you wouldn't know by observing from the outside.
This seems like a classic case of doing it being proof that it can happen, but not doing it being insufficient proof that it's impossible. I don't think there's a "quick test" of whether there might be a more effective prompt that would cause it to reproduce more effectively.
Didn't we get this with Harry Potter back in like gpt3.5? I'm sure I saw some news about it, someone getting it to output a book's intro word by word, couple pages?
if the original essay was stuffed within the prompt window. the result will be word accurate.
unless this is a model trained specifically on Micken's essay (which claude is not).