I received no mount into my bags after finishing the “Through the Depths of Visions” achievement. The achievement bugged out after finishing “We Have the Technology” but did not award me the “Through the Depths of Visions.” I relogged and the achievement was completed after logging in but I have no mount. I already checked Item Restoration to see if it was in there and found nothing.
I was going to suggest you open a ticket and let the Game Master team take a look at this, but it looks like you have opened a couple already.
The responses seem to indicate that this may be a bug that needs the attention of the World of Warcraft team. And that the Game Master staff is unable to grant you the mount as a result.
Is it a mailbox thing like what with the flame hippogriff from Cata?