Background to problem
I was using the Facebook comments social plugin without a Facebook application ID (on Drupal with Facebook social plugin module); it was working just fine like this.
I later decided to get and use a Facebook application ID from http://developers.facebook.com/setup/ to enable comment moderation.
Since I did this, however, all the Facebook comments that were entered onto my site before I used the application ID have disappeared.
I tried removing the ID from Drupal module (as it was before) but that made the Facebook comment box no longer load on my website (even though it worked before I got the ID) so the comments box now no longer works without the app ID.
The Facebook reference says that the default ID for the comments box is the URL-encoded page URL so I assume that the comments that were lost are associated with this ID and will no longer show if I am using a Facebook application ID.
This may be an issue with the Drupal module, I am not 100% sure, but I think it is more to do with Facebook's poorly designed implementation of the comments integration system.
Can somebody please confirm the reason for the disappearance of the old comments, or say what otherwise is the reason?
Is there any way to now get the old comments (pre-application Id) back onto my website (preferably while still using the newly obtained app ID)?