You will not be able to locate your Mercedes key by any means; however, the authorized Mercedes-Benz dealer will. They can also deactivate it and replace it with a new electronic remote control. It will permanently erase all traces of any previous information. Changing the mechanical locks is also recommended if your key is stolen; however, the mechanical key's robbery attempt would set off the alarm. It is preferable to replace both the mechanical locks and the electronic key simultaneously. This may be accomplished by visiting a Mercedes dealership in your region.