I have done that. I have also dropped it in other places. I have installed Phoca. I have cleared everything in firefox, tried other browsers... NOTHING..
I just did that on a site and it works.
May be you have to check rights for that file.
On your site I see a blue one?
You can also check you site with the webinspector in Safari or Chrome to show you the missing favicon as Joomla always trys to find one. Not sure what you mean with Phoca?
I have just come across this issue and in my searches found your post which prompted me to make my own post asking the same question in the 'Modulus' forum.