First, the guy who delivered the lumber for the side porch.
Second, a firefighter friend.
Third, the mailman who politely mentioned it.
So now I have a house number. Yes, I did use my kindergarten skills to trace around the house numbers Steve removed from the now-demolished front porch. I used a ball-point pen. The whole process, including the scribbly coloring-in, took about two minutes.
It ain't beautiful, but it serves the purpose.