The Manage Locks window does not list locks that are associated with your current Rational DOORS session, because you must not delete these locks. If you deleted them you would corrupt your data.
If you are a standard user, you only see the items that you locked in previous Rational DOORS sessions. If you are a database manager or a custom user with the power to manage the database, items locked by all database users are listed.
If you are a standard user, and you cannot see the locked item in the list, another user must have it locked. Contact your database manager to find out who has it locked.
If you have a chain of locks from the root of the database, you only see the lock at the end of the chain.