I would make sure they get paid. Unless you sent cash the payment method will show if it was cashed or accepted. You can place a stop payment on a check, money order or cashiers check if it hasn't cleared and reissue. If it was sent with Paypal or using your debit/credit card you can also determine if it was received and reissue. You need to initiate follow up with provider of payment form whether it is a bank, post office or other seller of money orders.