The retired botanist who showed me a fern growing in a parking lot in Detroit

I was walking out of a diner near Eastern Market in Detroit when an older guy with a canvas bag stopped and pointed at a tiny fern growing out of a crack in the asphalt. He said, "That's a walking fern, and it doesn't belong here." I asked how he knew and he knelt down and showed me the little tip of the leaf that roots and makes a new plant, so it literally walks across the ground over time. He told me he taught botany at Wayne State for 30 years and now he just walks around looking for stuff that survived where it shouldn't. We stood there for maybe 15 minutes while cars went by, and he explained how spores can travel on shoes or wind and land somewhere with just enough shade and moisture. I took a photo and went back a few weeks later but it was gone, probably from the street sweeper. It made me start looking at sidewalk cracks on my lunch break, and I have found all kinds of things since then. Has anyone else had a random encounter like that where a stranger totally changed how you see a plant?