gloomy meadow
I had a Falias Treasure in my pet inventory. I tried to equip it and the item went back into my pet inventory with a popup saying if I would like to use it and therefore bind it on my character. I clicked yes. It didn't automatically go into the Falias slot but stayed in my pet inventory. Now it's stuck in my pet inventory with no ability to interact with it besides destroy BUT I get the notification that I can't destroy this item.
I'm unsure if I placed the item back into the pet inventory slot or not before pressing the OK popup but that's something to be taken into consideration trying to replicate this bug.
velvet steppe