dealer keeping my second car key

Is this a buy here pay here place? If it is they might be holding the second key so they can come repossess it if the need arises. Read the paperwork that you signed. If you agreed to that, then they can hold the second key until the vehicle is paid for. But, depending on the laws in your State that practice may be illegal. Check with your local Office of Consumer Affairs to be sure. As a last resort, visit your local Ford Dealer and tell them you lost the other key. You want all keys removed from the vehicle's memory and only the key that you have plus the new one, you're going to buy, programmed to the vehicle. After that, the key that the Dealer has will no longer work to start the engine. Hope that helps! Jim