Could not find an object from another schema

When try to call to object without write the specific schema:

• dbo/db_owner/sysadmin doesn't find an object from another schema - because dbo/db_owner/sysadmin doesn't try to find objects in other schemas, Unless another schema is written Explicitly.
• Other Users/Schemas/Rools try to find the objects in their schema, and if it's not exists - they will try to find the objects in dbo schema.

http://social.technet.microsoft.com/Forums/he-IL/sqlhe/thread/9e3b2677-602c-4697-a0de-292929ebda54