How to locate account owners of external bank accounts throgh user interface

Summary:

When entering a bank account on customer B, we receive a notification saying thah the bank account is already in use. How do we locate the original bank account owner (Customer A) through the UI when we only have a bank account number?

Content (please ensure you mask any confidential information):

When entering a bank account on customer B, we receive a notification saying thah the bank account is already in use. How do we locate the original bank account owner through the UI (Customer A) when we only have a bank account number? They are not showing up under Manage Bank Accounts. Only internal bank accounts are shown here.