"orderdone.php" does not always print the final order confirmation page. If you use a self-hosted payment plugin, it prints the order confirmation details in "orderdone.php".
If you use an external payment service, this layout file redirects the users to the external website. In that case, the order confirmation page is displayed using -
components/com_virtuemart/views/vmplg/tmpl/default.php
You can add your desired div in this layout file by overriding it in your template.