Although the hot flop of the moment is the Amazon Fire Phone, remember that Facebook's had a few failures to launch a dedicated mobile, too. The first HTC devices were poorly received, as was the subsequent HTC First, plus the Facebook Home Android app has surely been abandoned. So... it's having another go?
A patent described as "Co-Molding Display with Body of Mobile Device" has been refreshed by the social giant (it was first filed back in 2011), featuring updated concept images and claiming to show a method of binding a phone screen to some sort of phone chassis.
That's all there is to go on, so we're quite a distance away from Facebook Phone Attempt 4.0, but it does show that some people, or one rogue person who doesn't realise the war is over, is still thinking about phone hardware inside the Facebook world. [Google Patents via Phandroid]