This information should contain the debtor's bank account information. In a loan situation the bank will issue a check to the debtor. The debtor will deposit the check in his or her bank account. As the check makes it's way back to the issuing bank the debtor's bank account number will be on the back of the check issued by the bank. If you subpoena the secured party for a copy of this check it will show the document trail including the name and account number of the bank the debtor actually deposited the check.
Most people are usually creatures of habit.
Once a banking relationship is established, it generally remains the same. Now, the above information may be outdated. However, there are two additional sources of records that the landlord has regarding the debtor's bank account. The debtor may have deposited this check in his bank account. The landlord or the landlord's bank has a copy of this check.