By "expunged" I mean disappeared from a takedown request.
If it's just a post being flagged and/or not approved, I can still go to the post and unfavorite it. And if it's in a favgroup I can find out the post id, edit the favgroup, Ctrl+F for the id and delete the number. But that doesn't work for ordinary favorites, since there doesn't appear to be a way to edit favorites as a plaintext list of post ids, the way there is for favgroups and pools.