Answer:
There are a couple of ways to get a key made without a key, or when one is lost. For a vehicle one can be made from a code which when decoded gives the cuts of the physical key.
Another way is by disassembly of a lock to determine the cuts.
Another way is by impressioning, when a blank key is used in a keyway and a mark made, then filing on the marks until a key turns.
Some vehicle keys once made might have to be copied onto a transponder key to let the vehicle run.
Locksmiths are usually pretty good at making a key on site when someone losses their key.