I have a question about the way Facebook limits your api calls.
Toward the bottom of this article: http://developers.facebook.com/blog/post/478/ facebook says:
There is no way to get more than the last 5000 objects, sadly.
Unless, as you said, you maintained it from a time when there were LESS than 5000, and stored them. :)
It may or may not be intentional (maybe they are trying to let old news die and not be found easily), or, it may coincide with the amount of friends you're allowed on Facebook, 5000.