So i went to Deepholme and found and killed Aeonaxx. he didnt drop anything.
I have 4 screenshots showing aeonaxx dead and red tagged boarder, my Details addon showing my dmg done to him, my combat log showing my dmg done, and my mount collection searching for the mount he drops, Phosphorescent Stone Drake.
When I got mine, I had the mount drop into my bags and mailed to me.
If you are sure that you were the only one to tag & damage it, first try a full UI reset (as detailed in Support Article linked below) to rule out a display issue.
If you are still not able to see the mount, then putting in a ticket might be needed.
You might be remembering the Bug Report forum, Razier. Though when there are realm or log in issues, we do collect some information to help look into those through this and our Technical Support forum.
In any case, it looks like you have a ticket open so a Game Master should be able to check our logs. If they can verify the kill they may be able to help recover the mount. Good luck!
We can’t use Screenshots are evidence, but they can aid in our investigations. I should note response times are a little lengthy at the moment, but keep your ticket open and a Game Master will get to you as soon as they can.
As a fellow mount collector, I wish you all the best on this inquiry. I know what it is like to have to wait so long to get the mount that you want to drop.