I can totally understand feeling that way. At the end of the day, what you’re hoping for is beyond what a GM is allowed to do. They are not really there to fix or otherwise bypass existing systems that are in place.
As for what a GM can do, there’s a sticky in this forum that helps to outline what GMs are typically able to help with which I’ll link below too.
But when a player experiences a bug for which there’s a backup system in-place (mailing the item to the person who received it), then there isn’t much a GM is going to be able to do.
It’s unfortunate that it happened to you, but the mount is still available to be farmed too (one which I’ve yet to get myself!) so at least there’s that!
Spotlight on: Game Master Help