Assuming the doors are unlocked

And your lost key worked on door and worked on ignition
You can remove the door lock cylinder and take it to a locksmith he can then cut a key for that cylinder and it should work for the ignition.
You need to remove door panel, remove the bar clipped on to the lock, then in the door jab there is a tab that you pull out, lock then can be pulled out from the outside.
As a heads up, look and feel around the front bumper area and rear, previous owner may have put a "hide-a-key" magnetic box somewhere, I always use them, mine is in the rear wheel well, in a cross brace.
I hate locking my key in the car...............and it is amazing how many times I do it, lol.