The Lost Princess of Oz by L. Frank Baum [Wizard of Oz #11]

In THE LOST PRINCESS OF OZ, Princess Ozma is discovered missing.  Four search parties are sent out, one for each of Oz's four countries. Dorothy and the Wizard's must find her. Meanwhile, Cayke the Cookie Cook discovers that her magic dishpan (on which she bakes her famous cookies) has been stolen. Along with the Frogman, they leave their mountain in the Winkie Country to find the pan.

Lyman Frank Baum (1856-1919) was an American writer of children's books, including THE WONDERFUL WIZARD OF OZ and thirteen sequels.  In addition to his Oz books, Baum wrote dozens of other books and short stories, often set in mythical lands.