I don't know anything about furry art and social conventions, but in the professional art world if a client orders and pays for art, and the post office screws it up, it's the artists problem, the client still paid for, and should recieve, art. It's the artists responcibility, the artist would have to re-do the piece, or refund in full. Since art valuation is so subjective, you can insure it for more than the client actually paid for it, that way if it is lost, and you have to refund the money, you still can recoup some of you losses.

This is how it's done in the Glassblowing world anyway.