I realize this is your first post to our message boards, young Wizard, but a good tip is to make your subject relevant to your message. A subject such as 'read message' is actually less likely to be read and responded to.
The Bazaar is shared across all Realms and Areas. A hat sold in Wu realm will immediately appear in all Realms, and to specifically answer your question, NO if the item no longer appears in the Bazaar in one Realm it will not appear in any other Realm - the hat is gone.
