It is just a bug do not fear.
If you want to use it in-game, set it as your default equipment, and then you will be able to use it in game. (You can remove if from your default equipment after a couple rounds, it will show up in the equipment screen ingame afterwards).
You can also still trade it and it will work correctly.
However, I don't know if attempting to heirloom it to +3 will work fine (Haven't tried it but will probably work).
It should be the Balanced Bec de Corbin Harafat.