Gem Store Exploit
I’m not sure what you’re describing here.
It is just a bug with how the UI displays certain Gem to Gold exchanges. The Devs are aware of it, and the correct amounts will be exchanged in-game.
You can read more about it in the Dev Tracker, or over in the API sub-forum.
Good luck.
If you lost gems but got no gold, I would hardly consider that an exploit…