Your point is logical, but all I'm saying is that it's not evident that Columbo was merely a car length or so behind him. He could have been several minutes at that point. It's not evident to me that Columbo saw the parked car one way or another. They wrote it a certain way simply that the vision of the key triggered a question or contradiction in Columbo's mind. I for one love episodes where extraneous incidents occur, and you're not quite sure what is important to pick up on. I'm sure we could all write different scenarios which we think are better than what was done.