It's not on any subnet that I can see - in the properties dialog (attached to the tweet) it only appears with a MAC address, no IP address. That phone is gone now - this morning there was a Sony Bravia and now there's full_ford.

Angry IP Scanner doesn't see any of the bad MACs when scanning the same subnet as my router (Netgear R8000, 192.168.1.*). The router doesn't show them in the Attached Devices page either. I also have an Netgear EX7000 range extender and it doesn't show any of them in its attached devices.