Steve, I don't think pilots should be let off - if, indeed, the item did fall within the banned size range.
Working for a B757 operator, we did our own engine oil check and replenishment. I had a flat screwdriver with the blade ground to fit nicely in the RD211 cowl flap. One day I was challenged by security but, when I explained, they let it through. I guess they could have confiscated it but they were sensible chaps.