Skelington only ever got that mount once. It was on Skelington actually.
Have I ever mentioned I don't have a single Brewfest mount either? Nor the love rocket. So to sum this up, I've been participating in all 3 events ever since they were implemented and am yet to see a single mount. AT ALL. Not one.
Every single run, I got a squashling and a hallowed helm. Never once did I see a mount. At all. No one ever got one in any of the groups.
I got two last year, one on a druid (useless eh?). Since I just started playing again today, I missed it, but I don't really care.
Also, if Gunner sees this: