We're aware of an issue that caused RAF & SoR mounts/pets to disappear. Should be resolved next realm restart: http://t.co/NsPu9wkJW5- BlizzardCS (@BlizzardCS) February 18, 2014
So it seems the mounts will be returning to players as soon as the developers can work out this bug. We've also heard reports that players who logged out while flying on RAF mounts are falling to their deaths.
This appears to apply to the Rocket, the Nightwing and the Zhevra as well as any other rewards received from refer-a-friend. WoW Insider has all their Spectral mounts from the Scroll of Resurrection intact, so the bug with that is clearly not affecting everyone.
Filed under: Mists of Pandaria