Linking is not a way to combine accounts together, it just means that you change the way in which you access your account.
If you Link your account to Steam this means that you no longer need to enter a password, you can just press "Sign in with Steam ID" as long as you have Steam open. However if you have another account that was only accessible via Steam, you'll no longer be able access it as you have changed the link. This can lead to some players believing that their account has been wiped, this is not the case.
If you have done this and would like to restore access to your old account via Steam you'll need to provide the username of the account you have linked to and the account you have removed the link from.