I don't own any wp devices. So this answer goes in kind of assumption and internet research. Anyone wants to correct any information, please do so.
Windows Phone 8 only Support MTP and has no Native Mass Storage Support. But you said, it is not even detected on Windows 8 , that is a bit confusing.
However, since Windows phone uses MTP, so only we need update the MTP library.
While searching on internet, I found out a blog that talks about it, and he can mount it. But on Mac . You can look here
So, for ubuntu, I would suggest to give a try to updated GVFS with MTP support. The article was written for Android 4.0+ devices which doesn't support Mass storage but only support MTP. You can have a look and instruction here. They talk about updating the MTP library.
But, interesting thing is, they have added a note on Feb 13, 2013. with a list of devices that are supported in the unstable PPA. And Lumia 920 is there. So it might be possible, it will be working with 620. If not you have to wait.
So I would suggest,
ppa:langdalepl/gvfs-mtp & install all available update.
Reboot, unlock your device and connect. See if it is now on Nautilus.
If not, add this unstable ppa
ppa:webupd8team/unstable & avail the updates. There should be one update,
libmtp. Install, reboot and retry.
The downgrade info is there on webup8 site. Remove
unstable ppa first and then