I believe Whispernet is a service, not an account; perhaps you meant your Amazon account? If you go to the "manage your Kindle" section on Amazon, you will see what eBooks you have purchased from Amazon. Only ebooks/newspapers/magazines purchased from/downloaded from Amazon will show on your Amazon account. Amazon, theoretically anyway
, has no knowledge of content you download to your Kindle from other sites.
Holly
Edit - Harry beat me to it!