The first thing to tell you is that all BMW models come standard with two car keys, and there may be a plastic mechanical key depending on the model. In addition, the X6 xDrive35i currently on the market has the function of keyless entry, that is, if you walk to the car with the key within an effective distance, pulling the door handle will open the car door, so it is theoretically impossible to lock the key in the car unless the key is dead. If you only have one key when you buy a car (which is impossible), you should go to the dealer and ask them to provide a second key, because it is standard.

good luck