Wow, that is a pain, Im sorry Jim. I would think your best bet is to contact the company and see if someone can track down a plan for you so you know where it is.
Taking a swing, just going of instinct, if there isn't a circuit for it by itself in the fuse box, it is probably part the circuit above it or closest to it. Most likely tapped in somewhere. May have to play "the test and turn off game" with a light and fuse panel to track down and figure out the circuit. Id then go to the closest outlet to it and pull apart and see if you see any wires running in that direction. Id also be tempted to pull up what you can around the area of the outlet and see if you can find the wiring.