We would have to take a look at your database to see what happened. Could you please perform a backup, compress it and send it to our support address?
Generally, most of the content is bound to the user that created it (pages, HTML editor articles, blog, wall and forum posts, etc.), and the during the removal process, all associated content is being deleted. It sounds like you deleted the user that entered the content the content, even if the default admin account is still active. In any case, we will be able to tell more after we see the database.