This happened to other people a week or so ago. If one book is gone, yet the others are there on your KDP Bookshelf/Dashboard, use the Contact Us option (bottom of this page, right side) to ask Support for help.
(Don't trust KDP to publish a print edition. Don't trust CreateSpace to publish an ebook. Each does one thing well and the other thing poorly.)
Hello there, I have the same problem, for the last couple of days books have been randomly dropping off my author page, luckily I have links to the missing books but i@m concerned about loosing sales at this time of the year. I have contacted support, waiting for a reply.
Hi there I've just contacted support again about the books missing from my author page, there's six in total gone adrift, one ebook and five print versions. I don't know how this has happened, I haven't made any modifications to the books and they were literally there on day gone the next. I've bookmarked links to them from my twitter feed and they are still there but I am concerned about losing sales to any potential customer taking a casual look at my author page and not seeing the full list of my titles.