I have researched the data issues and it turns out there is no way we can recover any of the missing icons through our records. FB have locked the door in a genuinely secure way. For once they have got their security right. What they got wrong was overriding their user's settings without their permission in order to lock us out of data their users had given us permission to use. Their excuse for this would be that the data was insecure and unsafe to allow us access to. But since I have established that this is actually impossible, it looks very much like the whole exercise either applies to data we are not using, and we have been hit by a process intended to deal with other apps (in which case it would have been easy for FB to identify that we should be exempt) or the entire process is literally for the sole purpose of inflicting pain on developers in public so that FB can be seen to be inflicting it.
At this point I think hell is a bit too good for whoever makes those decisions at Facebook.