Please see the picture attached. Is this what your key looks like? If so, I circled the "valet" key in red. Is this the key that you are referring too?
If the answer is yes to all of this, I have bad news for you. There is no way that metal key will start the vehicle. This key is not a "valet" key that you can provide to the valet and allow them to start the vehicle. The FOB that is lost is what has the chip in it that the vehicle recognizes in order to allow it to start. This metal key is only used to unlock the door if the FOB is lost or the battery is dead and the passive entry will not work.
I attached procedure on how to program a new key but unfortunately a dealer will most likely need to be involved.
Sorry to bring bad news tonight. Please let me know if I can help in any other way.
Images (Click to enlarge)
Saturday, April 13th, 2019 AT 7:31 PM