Redwall "Book 23" (lost unpublished children's novel; existence unconfirmed; 2010-2011)
Reisa Kartwell, by Sean Rubin. This image is currently the only piece of evidence to this work's existence.
Status: Existence Unconfirmed
In early 2010, Penguin Publishing House organized a contest (the rules of the contest are here) in which one participant would receive the chance to make a character that would appear in the next book of Brian Jacques' then-popular children's fantasy series Redwall. The winner of the contest, under the username Hyzenthlay of Redwall contacted the chief administrator of the Redwall Wiki, telling him that she herself had been contacted by Penguin and was told that she had years ago won the contest.
Her entry, a hare named Reisa Kartwell, was drawn by Redwall illustrator Sean Rubin and her illustration was mailed to her and uploaded to the Redwall Wiki. However, her character didn't make an appearance in the next novel of the series to be published, The Rogue Crew. Brian Jacques, the author of the series, was known for being very ahead of schedule and would work on many projects at the same time. This makes it possible that the character Reisa was intended to appear in an unpublished new novel.
Sadly, Jacques died on February 5, 2011, leaving his last written novel, The Rogue Crew to be completed by a ghost writer and published posthumously. To this day, the 23rd Redwall novel is either lost, unfinished, or both.