you must contact itunes support at expresslane.apple.com and ask them to put your audiobooks back in your que for download. you have no backup and they do not show up on the device for redownload. you will need to download them in itunes on your pc in order to get them back. itunes will send them back, you will not need to purcahse them again. make use you give them the order number from your purchased history for the audiobooks to cut down the time it takes for them to reply.