Audiobooks won't show in the cloud for redownloading, they are one-time only downloads - you will need to copy oy sync it to other computers/devices that you want it on.
For the music, are you in a country where music can be redownloaded ? If you are and some music isn't showing, then is it still in your country's store (record companies occasionally remove songs/albums) ? If it is then check to see if it's hidden : http://support.apple.com/kb/HT4919
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