Actually
Tolkien had quite a lot of notes on Savantsquatches, more even than on ME. He devoted one whole section of his personal library to his notes and sketches on them. Then as with so much of his notes and scribblings on ME, he died before actually turning them into a coherent Story. That is, it was left to Christopher Tolkien to make sense of them, or as
Bilbo might say, knock them into shape.
Christopher, ever respectful of his father's works, carefully looked over the notes and, one painstaking page at a time, burned them.