Found the Icon, No Problem Rated 4 out of 5 stars
I didn't experience the missing icon problem.
If anybody else has trouble finding the icon, it's probably "hiding" in the "other, non-default icons" section of the browser. To find those icons, see the article about customizing Firefox's toolbars: https://support.mozilla.org/kb/customize-firefox-controls-buttons-and-toolbars
I'm guessing the comment below was around the time when the "add-on bar" was removed from Mozilla Firefox: https://support.mozilla.org/kb/what-happened-to-the-add-on-bar
You can put it in your main bar, or install it from https://addons.mozilla.org/firefox/addon/the-addon-bar/
Closing notes: using Firefox 30.0 (current).