If one found notes of indebtedness, he should not return them neither to the creditor nor to the borrower.

If the creditor has the note, he can use the note as evidence that the debt has not yet been paid. If the debtor has the note, he can produce it to prove that the debt has been repaid. Thus, if the debtor does not admit to the loan, the note can't be returned.

Furthermore, a loan creates a lien on the properties sold by the debtor after the loan has been made. Even if the debtor admits to the loan, it can't be return, because the creditor and the debtor may have colluded to defraud the buyers of these properties.