It might become a costly undertaking considering that you will not only change the keys and reprogram your hardware, but also have to change the locking mechanisms on the doors to match the new key sets. Although the lost keys can still open the doors and turn the ignition, reprograming the hardware will prevent the engine from starting. Yes the thief can get in without popping the locks on the doors and the ignition, but keep in mind that some thieves can get through a lock as fast as you can put your key in and unlock the door anyways. But if I were in your shoes, since it's not my fault that the keys were lost, my brother inlaw will have to pay for the expenses!:thumbup: