Kindle Reader on Mac OS X Bug

I use Kindle heavily for reference books and normal books across many devices and for some reason, I always have issues with the Mac version of Kindle reader. For some reason my purchased books do not always appear in my library. These are the non-downloaded versions so I can't download them because I can't see them. I've found a fix that although can be annoying, works so far 100% of the time. All you have to do is go to Kindle > Preferences and then Deregister your account and re-register! Now all your books should appear in your library for you to download! I've had to do this a couple of times which is annoying but at least it works! Hope they fix this issue! Edit (June 27, 2014): Apparently, this happens on the Windows version too. You'll need to deregister as well and re-register to get all the books to appear again. Quite disappointing.