the validated entries binding is only populated when the form fails validation.
if the form passes validation, the form data is stored in session variables using the following naming convention:
eCartCheckoutForm_<element name>
where <element name> is the name of the form element.
you should make sure that the failed redirect in the server validation behavior on the confirm page passes a querystring variable, for example:
checkout.php?valid=false
then in the in initail value, use an isset() ternary expression to use either the validated entries, or session value, for example:
<?php echo((isset($_GET['valid']))?(ValidatedField("confirm","firstName")):(isset($_SESSION["eCartCheckoutForm_firstName"])?$_SESSION["eCartCheckoutForm_firstName"]:"")); ?>