Misplaced my iPhone in my house. Battery is dead.

Well, if the battery in your car has run down......the car won't start.

If the batteries in your flashlight are dead.....there is no light.

This is not too technical. We could give more examples, but I think you get the idea.

The phone can't walk or run, so you should be able to find it in your house.

So, you really are asking how the phone.....or any other electronic device......can send or receive a signal when the battery has run down?

You retrace your steps and look for it the old fashioned way.