Yes, without a hundred (more or less) generations of monk-scribes to recopy the Red Book of Westmarch, its pages would have crumbled into dust and we know that the fan-base didn't stretch that far back into the mouldy recess of time for that to have happened. Therefore, J.R.R. Tolkien thought the story up all on his own.
That is not to say that the ghost of Bilbo Bagins hadn't been leaning over the professor's shoulder, posing certain leading questions to draw out those particular events from Tolkien's imagination, which he later fleshed out on paper for our enjoyment. :teacher:
'Share and enjoy'