Make sure the dimmer wheel is not clicked into the "inside light" position.
That's just my first guess. If that's not the case, some Fieros (through 85, anyway) had a button in the overhead that would turn on the center map lights. (And maybe the footwell lights?)
Barring all that, I have seen strange "alternate paths" - especially in GM cars - happen when fuses are blown. Is there anything else that is not working? Radio memory? Lighter? Trunk light?
All SWAGs, admittedly.