At this point, the marketplace is only facilitating the match-making between buyers and sellers while the payment is happening only via the wallet. In addition the marketplace does not get feedback from the wallet whether the amount is paid or not, which is why there is no function at the marketplace informing you about the payment status.
Nevertheless, that might change once we are working on an integrated payment API, which is scheduled for later this year.
For now sellers need to check in the wallet, whether a payment has been received. To make the check-up easier, item numbers which are communicated through the order confirmation emails will automatically be associated with the payments in the wallet.