As he posted the ball and he will or would of had the tracking number he is the only one that can make a claim through australia post as he is the sender. if australia post have lost the item and as he is the sender and the only one that can make the claim i say that he has to refund you the money back for the ball . if he has lost the tracking number that is his own fault.
resurgence refund the amount on the ball to bulldoza and make the claim yourself.if you have lost the tracking number YOUR FAULT