The visible HIN on mine is just below the exterior rub rail and to starboard of the transom boarding gate.
I've heard this tale of a hidden location for a HIN, but after 15 years of ownership where I've been almost everywhere onboard, I've never found one, but I wasn't really looking for it either.
If you remove a drawer or two, say from below any of the berths, you will likely find on the bottom or back of the drawer, in black felt pen (likely put there by Tollycraft's cabinet shop) at least the numbers 57-0XX, which will be the sequential hull number.
Beyond that, I'm of no further help, but let me know should you actually find a Hidden HIN.