I earned the Elemental Horse Kelpion mount last season and while I understand that it expires at the start of this season. I cannot repurchase the mount (it shows as unavailable with 0/1). My understanding is that one needs to re-earn the mount by achieving Supreme 1 in the current season and purchasing the mount again (hence the label “seasonal roster limit”).
However, it might be that the mount was accidentally coded as “roster limit” instead of “seasonal roster limit” and thus is unattainable for those who purchased it in the previous season.
I checked my mount list over and over and could not find the mount in question in my list. I am currently Supreme 6 this season and I reached Supreme 7 last season.