... try this in your 'order.php' or 'page_header.php'...
... add after ...
$site_template->register_vars(array(
... this ...
"loggedin_user_name" => ($user_info['user_level'] >= USER) ? format_text(trim($user_info['user_name']), 2) : "Guest",
... and use in your 'order.html' ...
{loggedin_user_name}