Originally Posted by DoctorOhh
I do not have a Kindle and have never used a Kindle, as such my advice might be tinged with a touch of ignorance. Have you tried shutting your Kindle down and turning it back on? If that doesn't work I would suggest deleting all of the books on the device via calibre's device view then resending the same books to your Kindle as previously instructed and you will see all of the books on your Kindle again.
The Kindle may need to be Restarted (not the same as turning OFF then ON). A Restart will initially show the Kindle Tree logo and rebuild the book list.