Hi, 1more, let me see if we can clear up what's happening here.
I'm assuming as you say you have a Kindle HD that you mean a Kindle
Fire HD - yes?
When you go into 'Books' on the Kindle and click on 'cloud' the book's image is still there and if you press on it, you get the option to download it? If this is true then, as Ann says, the book is still in your Amazon account.
The only way to delete the book permanently from your account, is to go to the Amazon website and log in, then go to your 'manage your kindle page'. If you buy your books from amazon.co.uk that's
here or if you use amazon.com, then it's
here.
Once you're on that page, you should see the book listed - use the search box if it doesn't show up at the top of the list.
Once you find the book, use the button on the far right of the screen that says 'Actions' and that will give you the option to either delete the book from your library or to return it for a refund if you've had it less than seven days. Either option will remove the book from your account and from the cloud list on your Kindle.
One other thing to consider - when you perform the sync, are you sure your wi-fi connection is working and that the Kindle is actually connecting and updating?