GM has just updated client to fix pet issue & this Bunny Ribbon issue. So please make sure to update your client. If you dig in the gacha field after this update, and if you get this item, it will appear (become visible) in your MyShop inventory now.
However, for those people who have gotten this item BEFORE this update, please wait for a bit longer for the item to appear in your myshop. The fixing of this issue falls to Coder and he has not made the fix yet (for items obtained before GM's latest client update).
p/s ~ pls don't ask me why GM does not fix everything at one time; Idk how he and Coder divides their work.