Heaven and hell in one extension Rated 1 out of 5 stars
I like the idea of getting the favicon back in the address bar, but I can't stand the old "blank document" icon so this is worse than useless to me.
A blank page is intuitively "something" and gives the impression it's associated with the content. A dashed square using no additional colors beyond the tab's own background color implies that the icon itself is missing (like one of those "glue photo here" squares on a professionally-printed form or photo album), which is the correct implication to give. (The blank page icon, if anything, should be used only for about:blank)
Site Favicon in Urlbar
Since Favicon Restorer doesn't match your needs, give this other one https://addons.mozilla.org/en-US/firefox/addon/site-favicon-in-urlbar/ a try.