On Facebook when accessing messages, you can change the message id in the URL and see for any message who it is posted to.<p>e.g. try this in your Facebook account: https://www.facebook.com/messages/503348860
or see a screenshot here:
http://postimage.org/image/a6w7x76yv/<p>It doesn't show the message so I can't think of a serious problem but I'm not sure I should be able to see who a message was posted to.