The dealership is brushing you off, which is sad has already happened to me, so my advice - Might need to find a new shop.
- Having been victimized myself - the effort of re-cutting the key for the tumbler can be left to a dealer or repair shop - you'll have to discuss options with them.
- The issue of RF Actuator (the receiver in the car which takes the commands from the key-fob) it usually is safer to have the shop disable or remove the actuator and leave it with you, while you use the manual options of the key in the door and to start it, until you can be assured from those involved that the keys are "gone" - then it may be possible to have the actuator reprogrammed - but in light of your thoughts on this subject - any vehicle over 250,000 miles is quite a feat and to be honest - a liability even for those whom steal cars, for if it broke down you may get stuck with the bill to clean this up - fortunately it sounds like it didn't happen.
It's not that Ford can't find them, they have moved on since then and now they can't provide the parts or support for them anymore - they simply stopped making the parts.
For Ford itself though, they don't support the Fiesta as much as they once did - even on my latter model of yours. So I'm already looking for aftermarket support that Ford has left sitting on the table.
You realize that being juveniles, they will have tried to "lose" those keys intentionally but might remember to know where they were lost at, as they can try to go back and retrieve them at a later time once they are freed of the scrutiny. So they will be more than likely going back - tracing their steps - to where they pitched them. If the police had them, they would have already given them back to you, else you may need to file a report follow-up on the location of the missing keys, as if they are being used as evidence for the prosecution - then getting them back may take a while.
