I feel as though the title of the book may have been along the lines of “The Last Unicorn” – but that book that comes up in my internet searches is not the correct book. (The over 50 year old book that was made into a movie about the unicorn looking for more of her own kind is not the correct book.)
Unicorn picture book, black and white drawings, no text
My kindergarten library had this book in 1985, and it did not look new. It was a red hardcover that was much thicker than other children’s books. I think the title included the word “horse” or “unicorn.” The story was about a little girl who finds and then hides a white long-legged foal that develops wings and a horn, but there was no text; the entire story was told in detail with lovely black and white pencil or charcoal illustrations. I remember it being relatively sad, with the unicorn flying away/escaping in the end.
I wish I remembered more! I’ve checked my kindergarten’s digital library catalog with no success, as well as other online catalogs, but there are so many unicorn and horse books out there!