How to translate a ORIGINAL_LOGIN() to its database user name?

My Original_login() is a windows account.
use [master]
select orginal_login()
Return:TFHGFHG-2005C97Administrator
select user_name()
Return:dbo
But following code returns nothing in MASTER database:
---------------------------------------------------------------------------------------------
SELECT a.name,b.name AS Login_Mapped_to_DBO
FROM sys.database_principals a
INNER JOIN sys.server_principals b
ON a.sid = b.sid
---------------------------------------------------------------------------------------------
But it can return a row when I run it in a user-created database:
Return: dbo TFHGFHG-2005C97Administrator
How can I translate a original_login() to a db user name?
Thanks for any help.