[GAMEPLAY] Elixir doesnt disappear from inventory

I bought a blue elixir as Lissandra, saved it for later in the game (sat at my last item slot). Finally used it, took some towers, and then backed. It may have expired by then. Anyway, i hit my shop, and sitting in my last item slot is my elixir, even tho it doesnt show up in my inventory outside the shop. So i sell it, and it gives me money. This seems wrong.