It is possible that the car is fitted with an aftermarket add-on device(eg for I pod)that has been looped into to fibre optic system.Is the car fitted with 2 cd multi changers in the glove box?May be an idea to drop this lot out to see if there is anything behind.As far as ckecking the f/optic system ,you should be able to see the I/red generator red glow from the optic source.hth