If there are transactions allocated to those bank accounts they are unable to be deleted for historical reporting purposes. However, they can be made inactive and I wonder if this might be the reason you are no longer able to see them in the Chart of Accounts? If you tick the option 'Include inactive' at the bottom of the list are you able to see the missing bank accounts with an X in the left margin? If so, hover the mouse over the X and click to reactivate or rick-click and select 'Make Account Active'. Hope that helps.
Reckon Accredited Consultant