n3 The majority opinion recognizes that if, after improperly exercising a setoff in violation of section 726, a bank refuses a debtor's demand for the return of the setoff funds, the bank would be precluded both from foreclosing the security interest and from proceeding on the underlying debt. (See maj. opn., ante, p. 1006.) The opinion concludes, however, that a similar complete sanction is not warranted when, as here, the debtor does not request the return of the offset funds but maintains that the improper setoff itself operated to waive the bank's security interest and its right to collect the balance of the underlying debt.