Honestly, I haven't looked closely at the latch mechanism to tell you how to UN lock it. However, the lock is accomplished by a metal pin that engages a small plastic piece. That small plastic piece (according to this) is far from expensive. You can probably find enough change in your seats to replace it if you have to bust the thing open.
It also looks like the solenoid is held in place with a single screw, so if you get behind the carpet there, it should be pretty simple to pull the whole deal out.