I'm not sure if a dealer can flash over it, you might want to check. I've heard yes and I've heard no. If they can you would probably have to pay a couple of $$$. When this happened with my son's car the dealer estimate was between $500-$800 worse case was an ECU replacement.
You could also look for a used ECU from a junk yard or for sale forums here. Then you can send that one in for unlocking. Or maybe consider enterprise for a weekly rate rental.