I don't think anyone at USPS will be able to help you.
Have you emailed Mike B. directly? (mike@avalanchepress.com)
Did he respond?
I've been ordering American stuff from across the Pacific for 8 years... sometimes things just don't make it. Fortunately, the merchants have always shipped a new set out of the goodness of their capitalist hearts.
...came for the cardboard, stayed for the camaraderie...