Well, had the officer not been lucky, he'd've opened the trunk and found nothing. The stop would presumably end there¹, and so too would any discussion of the legality of the stop unless the person whose rights had been violated had the time and resources to pursue the violation "on the principle of the matter"… not something I think most people are going to have the resources to do.

So I wonder if we could be seeing a bit of survivorship bias.

¹though with cops you never know