Rather, if using the item required an attack roll, then that attack roll has the capacity to contribute to stress inflicted (and in this case, did).
It is possible to create an enchanted item that attacks without requiring a roll on the part of the user, simulating a 'bottled' Thaumaturgy attack, but that wouldn't have a weapon rating, and is typically... less than optimal. (it's also irrelevant to this case, as an attack roll was required, or at least made; I just thought it was interesting to note)