I'm trying to tell Dad what it was because I was showing him the pictures. I said it was Jessamine and he said, "In West Virginia, we call that jasmine." And then I had to explain how they're different things. This is why I hang out on ATP. Talking to non-gardeners can lead to frustration.
I have smelled it at night so one of my neighbors must have it. I wonder if a bird or other critter brought a seed to my yard. FYI, it happens to be growing right next to the pokeweed which also mysteriously appeared a few weeks ago. That area is just a hotbed for volunteers!