Issue:

use [MyDB]
exec sp_dropsubscription
@publication = N’pbMyDBSnapshotPull’,
@subscriber = N’YYY\MyDBX’,
@destination_db = N’MyDB’,
@article = N’all’
GO

Result
Msg 20032, Level 16, State 1, Procedure sp_MSdrop_subscription, Line 85
‘YYY\MyDBMOBILE’ is not defined as a Subscriber for ‘YYY\MYDBINSTANCE’.
Msg 14070, Level 16, State 1, Procedure sp_MSrepl_changesubstatus, Line 1210
Could not update the distribution database subscription table. The subscription status could not be changed.

Solution:

use [MyDB]
exec sp_dropsubscription
 @publication = N’pbMyDBSnapshotPull’,
 @subscriber = N’YYY\MyDBX’,
 @destination_db = N’MyDB’,
 @article = N’all’,
 @ignore_distributor=1   –<<<<<<< *** Fix ************
GO

Result

The Subscriber was dropped.