title: User Notifications - How to recover a lost notification_id from GCM?
body: <p>I generate <code>notification_key</code>s as described <a href="http://developer.android.com/google/gcm/notifications.html#gen-server" rel="noreferrer">here</a>.</p>
  
  <p>Suppose that due to some error I fail to store it, so I try to re-register.<br>
  This time I receive a 400 error with the message <code>"notification_key already exists"</code>.<br>
  This looks odd, especially compared to <a href="https://developer.android.com/google/gcm/client.html#sample-register" rel="noreferrer">registration of a device to GCM</a>, where you can register as many times as you want and always get the same Registration ID with status 200.<br>
  Now I can't register again, and I also can't unregister, because I don't have the <code>notification_id</code>.
  <br><br>Is there any way to get the previously generated <code>notification_key</code> from GCM?<br>
  Or is the only way to register again with a different <code>notification_key_name</code>?</p>