Special Characters in a Table Name

The last day we accidentally changed a table name from 'dbo.TableName' to 'db.TableName'.

Afterwards we were not able to access the table at all, although we could see the table on querying sys.objects or INFORMATION_SCHEMA.TABLES.

The first impression was that the table schema/ownership got changed from dbo to db. However, the table was still existing in the same dbo schema but the name of the table became 'db.TableName' from 'TableName'.

Thus to rename the table I used the following command.
EXEC sp_Rename 'dbo.[db.TableName]', 'TableName'

Please note the use of [] brackets. It is used to embed special characters in the SQL Syntax.
Also, in the second parameter we do not specify the schema/username.