I also experienced this issue as the Stone Scholar. Typing 'use Vertebra Stone', 'equip Stone Staff' or variations thereof didn't do anything.
Ok that makes sense, the dialog didn't indicate that the staff was already equipped or that the item had no use ("That's already equipped" or "You can't use that here"kind of things).
It's not a serious problem, since I managed to die of infection in the Pauper's Catacombs without any bugs or glitches, A+