My antitheft light keeps blinking rapidly

Unfortunately you need to be towed to your local Ford Dealer for repairs. Not having a fob makes no difference in this situation. The computer is no longer recognizing the key. Also, on a Ford product you need two working keys to be able to program additional keys to the vehicle yourself. Jim

Before you go through the dealership nightmare try a locksmith, call around and see if some place has the equipment to check and see if it is the security system malfunction or just a bad chip in the key. Another thing is if it has the keyless entry keypad you can push the 7/8 9/0 buttons at the same time, wait 2 minutes then enter the code you have to unlock the car, usually this will put the security system into standby mode, and you can start and drive the car. If none of that works, then you're stuck with a tow bill and the dealership's ridiculous prices.