AFAICS Hermetic invisibility magic does not just destroy iconic species, but replace them with others which still provide an image: only a specific image, like the magus turned invisible, is destroyed, while the image of the room he is in is just altered.
So a standard (ArM5 p.144) Discern the Images of Truth and Falsehood of level 25+ should detect a standard PeVi 20 (ArM5 p.146) Veil of Invisibility.
I didn't read the 25 pages of this thread. So please forgive me interfering on just a technicality.
Cheers