In the new version of Sitecore, all user accounts were re-created.  That means your old account along with the old account favorites have been replaced with your new account.  Think of this as when you get a new computer, your internet favorites stay on the old computer and you have to re-create your internet favorites list on the new computer.

In the future, you will be able to add places in Sitecore to your Sitecore favorites.