The actual radio reciever (where the antenna plugs into) is located directly behind and below the glove compartment. (look for a little silver colored box with heat sink fins on one end of it)
Where you actually turn on the radio and use the buttons, is just the radio control module...... it is not the actual radio.
Odds are if someone installed an aftermarket radio, the reciever may have been removed from behind the glovebox... or it might still be there - depends if they took it out or not.
