Where a negotiable receipt has been issued for grain, no seller’s lien or right of stoppage in transit shall defeat the rights of any purchaser for value in good faith to whom such receipt has been negotiated, whether such negotiation be prior or subsequent to the notification to the warehouseman who issued such receipt of the seller’s claim to a lien or right of stoppage in transit. Nor shall the warehouseman be obliged to deliver or be justified in delivering the grain to an unpaid seller unless the receipt is first surrendered for cancellation.