Hello,
Like Nicolas explained ; The bank transfert details are currently only in the "order creation notification" email.
If you open that email ( HikaShop > System > Email) you will see in the "preload" part of the email the content ; it starts with:
if(in_array($data->order_payment_method, array('banktransfer', 'check', 'purchaseorder'))) {
The idea for your would be to remove the code from the email creation preload and copy it into the order status notification preloads.
But, please note that some modification would be required in that copy/pasted code since the structure of the data between the two emails is a bit different.
Regards,