Reply #19: I think that can easily happen when you don't have a visual reference point

[pinboy3niner]

You only saw the cars getting closer together. If you'd looked out your side window, a stationary reference point would have made your movement obvious.

Without a reference point, your brain interpreted the movement based on what you knew: you were stopped, with your foot on the brake; therefore, the other car must be moving.

I think you're okay. The time to worry is when you post this OP all over again and you're sure it's the first time. :)