I can't find them at all in the UI. Not the store, just where my current ones are.
Where is the heirlooms box?
Do you have the heirloom box? You can click on that to see which ones you have. There's a way to see them from your inventory as well, I just forget how to get to them. I kept clicking around until I found them..
Heirloom was part of the previous version of the game. This is no longer existing in the latest version.