What is the effect when the teller gave the passbook to a wrong person?

If the teller gives the passbook to the wrong person, they would be clothing that person presumptive ownership of the passbook, facilitating unauthorized withdrawals by that person. For failing to return the passbook to authorized representative of the depositor, the bank presumptively failed to observe such high degree of diligence in safeguarding the passbook and insuring its return to the party authorized to receive the same. The bank’s liability, however, is mitigated by the depositor’s contributory negligence in allowing a withdrawal slip signed by authorized signatories to fall into the hands of an impostor. (Consolidated Bank and Trust Corporation vs. CA, GR No, 138569, September 11, 2003).