Yesterday, after receiving the initial 1500 tenders from the Trading Post chest I bought the Celestial Steed. Opened the gift box in the mount journal and even rode around Stormwind on it for a while. About 10 minutes or so after Blizzard shut the Trading Post down. Today when I logged on to buy some cosmetic items with the remaining 600 tenders I had, I noticed that I no longer had the mount in my mount journal (was greyed out again) and I still only had 600 Tenders, meaning that I had paid for the mount, lost the mount but not been refunded.
I tried to open a ticket but Blizzard have butchered the support page, so trying to open a a valid ticket is like having teeth pulled.