It hasn’t been removed, I can guarantee that; there have been multiple guildies of mine that have received the mount in 8.3.
Unfortunately, I never heard them speak of problems such as the OP had.
In this thread, they said it was fixed in February; one person did report the bug in June. Nothing since.
Apparently if you have a toon with stealth you can work around this bug. I know, not much help for your warrior … but maybe a potion or something? Check comments in that thread.