There is a common understanding the solution must have been "Honi soit qui mal y pense", which was mailed in by several gamers, but the publisher never had the intention to pay the price in the first place, and therefore never released the "official" correct answer either.
Many players believe the solution was "Honi soit qui mal y pense," which they sent in, but the publisher never planned to pay for it and thus never released an official correct answer.