Hah, an interesting question and certainly not stupid at all!

A quick Google search [1] suggests that a (standard?) solar panel absorbs ~2/3s of the light, so it probably reflects enough to make out the car on the road. But the question actually becomes valid and important once we discover solar panel material that can absorb even more light (think Vantablack-like absorption).

Very good question!

[1]: https://news.rpi.edu/luwakkey/2507, search for "absorbs 67.4 percent" on the page