Except as provided by subsection (b) of this section, a consignee entrusted with and in possession of a possessory document is considered the true owner of the goods described in the document for the purpose of any contract with a third person for: The sale or disposal of the goods; or The pledge or deposit of them as security for any money or negotiable instrument advanced or given on the faith of the possessory document. A contract, pledge, or deposit described in subsection (a) of this section is not valid if the third person has notice that the consignee is not the true owner of the goods.