operating purely from emory, so apologies if way out, but search your hard drive (syste folder/hidden files INLUDED in search) for files that start something like "favicon.ico".
You may find a backup or similair collection, especially if you use more than one log on with Windows, if they have similair collections of favourites.
[edit] Did you recently clear your net cache by any chance?
Haven\'t tried it myself, but check out entry #108
here for saving/restoring favicon s....