Would you be surprised to open your car door and find a rock in your car? I mean, if you didn't leave one there the last time you drove. I was puzzled by the rock I found in my car. It hadn't been there the last time I looked. Sometimes Bron borrows my car, but why would he put a rock in it, especially on the floor of the driver's side?
It could be to put behind a tire to hold the car in place in case it's parked on a hill and the brakes give out.
It could be to break out a window in case the car plunges into a deep body of water.
Maybe it's intended for use against a car jacker... although a car jacker just might see a bright white rock coming at him. Yet ducking might not work to totally avoid injury, since rocks are prone to follow the law of gravity, and so could still fall on an attacker's head.
Perhaps it's really a petrified dinosaur egg.
There could be a diamond hidden inside.
Maybe it's an alien skull.
It could be ballast for an unexpected boat ride, or be used to hold down the corner of a tent constructed from the blankets I keep in the back of my car.
I finally asked Bron about it, and he said, "I saw one of those flags the Scouts stick into lawns tipping over, so I found this rock and used it to hammer the flag back in. Then I put it in the car and drove home."
Mystery solved! Now I can write a story about some of the things I contemplated before finding out the truth.
What did you think the rock was for?