Windows Server 2008 changed to Workgroup membership - Now can't login

One of our techs changed the membership of one of our Windows Server 2008 servers recently.  He changed it to a workgroup membership (supposed to be temporary while setting this up at a remote location).  However, he did not setup a specific local account to be able to login with before he changed it to a workgroup.  Now we can't login at all.  When the server was originally setup, it was joined to the domain during setup.  So I don't know that there is any local Administrator account on that computer.

If there was, wouldn't the user name be: "Administrator"?  I can guarantee that if it existed, no one has changed it.  But it doesn't appear that the local Administrator account ever existed because of the fact that the server was joined to the domain during setup.

The server has no access to Active Directory on the original domain - and it wouldn't matter if it did since it no longer tries to authenticate with AD.

Does anyone know of any other default account that might be used to login in a scenario like this?  Shouldn't Windows make sure there is some kind of local user account that can be used to login when changing from a domain to a workgroup?  This is a rather critical server and would be a real pain if we have to resort to wiping it and reinstalling everything!  Help!