I had a similar problem lost my keys, but if the keys are the original ones for the car then call up ford and give them the VIN no of the car and they will be able to cut you a key. May be pricey if your getting one with a immobiliser though!
I had 2 keys, one for the ignition(original) and then a different one for the doors which was off a different car, i lost the ones for the door and so couldnt get one cut from the VIN number of the car...so I had to break into the car then take the locks off and dismantle one of the locks and when u dismantle it your able to get a 6 digit key code shows you how here
GUIDE, coding your keys and rebuilding your locks : Guides / FAQs | Fiesta Forums and then u can call up ford and get one cut from the code...that was for a MK4 fiesta though so bit older..but im sure the basic principle is similar!