The bracket came off the actual seat? I thought you meant the floor underneath. In that case definitely not for a cd changer, only thing i can think of is its a mount for a power motor if it was going to be added as a option at the dealership, sort of like how some cars will come prewired for fog lights. Someone with full power seats needs to post a pic of the bottom of the seat.
Edit: i have lumber adjustment the motor is mounted to the rail on the driverside. Looking at the pic you posted it doesnt even look possible for a motor to be mounted. Im stumped.