Why was the firefox icon previously at browser/icons/mozicon128.png removed and is there a replacement?

I'm on Linux and have manually installed Firefox and set it to auto-update. After the update to v59.0.1 (64-bit) was applied, the application icon disappeared. Upon investigation, my firefox.desktop file was using the icon previously at firefox/browser/icons/mozicon128.png. I downloaded the tar from Mozilla's website for v59 and confirmed that the browser/icons directory does not exist. I then downloaded the tar for v57 from https://support.mozilla.org/en-US/kb/install-older-version-of-firefox#w_i-still-want-to-downgrade-ae-where-can-i-get-the-previous-version and confirmed that the icon file was included in that release. I checked the release notes for v59.0 and v59.0.1 but couldn't find anything relating to icons. Are the icons included in the new relase, and if so, where? Thanks!