function custom_wpcargo_trackform_shipment_number_query_callback( $sql, $shipment_number ){
	/*
	 * By Default here is the sql query
	 */
	$sql = "SELECT `ID` FROM `{$wpdb->prefix}posts` WHERE post_title = '{$shipment_number}' AND `post_status` = 'publish' AND `post_type` = 'wpcargo_shipment' LIMIT 1";
	return $sql;
}
add_filter( 'wpcargo_trackform_shipment_number_query', 'custom_wpcargo_trackform_shipment_number_query_callback' );