Hi Sean,

If you have upgraded to 1.2.12 you wouldn't have to replace the "config.php" file anymore. I have restored the file to the one from the 1.2.12 package for you.

Also, while you may have upgraded, your server is still serving cached old stylesheets.
I verified this by simply renaming "frosty/style.min.css" to some other filename, and tried to download the stylesheet from your site. I was able to download the stylesheet even though the file is actually non-existent.

If you are using Siteground, inspect their control panel for any area where you flush of disable caching (Siteground Supercache? Varnish?).
If you are using Cloudflare, you will need to purge Cloudflare cache from their control panel.

There is not much to be done from Joomla backend now, this cache issue lies within your web host / server configuration.