You still owe the debt to the individual's estate. The obligation to repay does not die with the creditor or no one would ever lend money out on the risk that if they die it's a gift to the borrower.
If there was no Will, a survivor, usually one who would inherit in the absence of a Will, would have to go to court and seek to be appointed Aministrator of the deceased's estate, make a demand on you and if necessary, sue you in the name of the estate to collect. Who knows, the deceased also may have owed others money and so anything you pay in would essentially go to the estate's creditors.
If you knew there were say only 2 surviving children and no claims, you could work out a deal to pay the 2 kids a portion of the amount owed, and avoid their need to file for probate, assuming they would otherwise not have to go thru that expense. You'd explain there are risks to you in paying them, should other creidtors turn up, that becasue of that risk you would expect a discount, and still insist they agree to indemnify you should there be other claims (such as from the deceased's creditors, other heirs that may become known in a Will you all are unaware of, or tax authorities) to the money you pay them.
