My opinion is that in a trade each person is responsible for delivery of the chip(s) to the other party. If the chips that were mailed were not received then a replacement shipment should be made if the same chips are available. If the same chips are not available, an arrangement acceptable to both parties should be made. That may be return of the chips sent to you, purchase of the chips the other party sent, or a trade of other chips if agreeable to the other party.
Paul