<pre><code>
function getIdFromMeta( $meta_key, $meta_value ) {
    global $wpdb;
    $pid = $wpdb->get_var( $wpdb->prepare("SELECT post_id FROM $wpdb->postmeta WHERE meta_value = '$meta_value' AND meta_key = '$meta_key' ORDER BY post_id DESC") );
    if( $pid != '' )
        return $pid;
    else 
        return false;
}
</code></pre>
it is work fine for me
this solution give me [Rochester Oliveira][1] my question on [stackoverflow][2]
Thanks Rochester Oliveira


  [1]: https://stackoverflow.com/users/609870/rochester-oliveira
  [2]: https://stackoverflow.com/questions/5450092/how-to-get-post-id-from-post-meta/5467348#5467348
this return post id but i needed nav menu id