As of today (29/11) it seems like this is bugged; I achieved gold on my main a month ago. When I entered LFR on my druid today I got DC, logged back, to found the chest from Challenge Conq: Gold in my bag. Tried on all my chars, even below 90 (worked as 48 as lowest since that is my lowest char)
So all you do it:
Have it on main
Enter ANY dungeon (you get DC)
Log back
Enjoy gear and ALL Phoenix mounts :>