SQL Server: Error while alter the schema owner to dbo

This issue occurred during my orphan users cleanup.(https://sqlserverrandoms.blogspot.com/2018/03/cleaning-up-orphan-users-and-finding.html)

While deleting one of the orphan below exception happened. 

Msg 15138, Level 16, State 1, Line 6

The database principal owns a schema in the database, and cannot be dropped.

Then I tried alter the schema to dbo and got below error. I didn't see the schema physically under Schema tab in Security of this database but this orphan is assigned as owner of database schema. 

Msg 15151, Level 16, State 1, Line 4

Cannot find the schema 'domain\login', because it does not exist or you do not have permission.

When I right click this user I see below mapping!

Now I was playing here and there and finally right click the schema to check what I am searching and found this orphan user as owner of those schema. 

Changed it to dbo and then I am able to delete this orphan user.