Of course we didn't see it as it sailed past the office windows :)
It's designed to only give a radar profile of a small fishing vessel.
My own personal theory is that this is all bluff, and it isn't like Eliot Carver's stealth ship from the James Bond film Tomorrow Never Dies. The trapezoid panels are just hiding a normal ship's superstructure. You tell your enemy that you've got a few of these craft, and he wastes ordnance taking out the local fishing fleet.
