Returning outstanding money to the creditor

I have taken/borrowed some money from a shop as I do not have enough money. I told the shopkeeper that I will give you the remaining amount next time I come, so he agreed and he further reminded me to pay otherwise on dooms day Allah will ask me about it. I didn't give him the remaining amount but now few months later I visited his shop to pay the remaining amount but the shop has been closed. When I asked about him from some of his neighbour's shops, they told me that he has closed his shop from here. I want to pay him his remaining amount. Can you guide me what I have to do?