Hi @aemninja
If it's accessible in publish instance then it's not an code issue and it's limited to dispatcher configuration only.
You will need to see what is the path that is requested to load the favicon and if the path is allowed in the farm file on the dispatcher /filter section
Also you can check in th dispatcher.log what error you are getting when you are trying to access the file directly. This will help you in debug the issue and you will be able to find the RC.
www.something.com/favicon.ico or www.something.com/something/something/favicon.ico
Thanks!