GetLastRecurringOrderID.php

<?php
$last_recurring_profile_id = $_SESSION['checkout']['last_recurring_profile_ids'][0];           
$customer_id = Mage::getSingleton('customer/session')->getCustomerId();
           		
$order = Mage::getResourceModel('sales/order_collection')
->addFieldToFilter('customer_id', $customer_id)
->addRecurringProfilesFilter($last_recurring_profile_id)
->setOrder('entity_id', 'desc')
->getFirstItem();
?>