Happened to me a few years ago on AA, morning flight DSM-PHX-ONT or FAT (can't recall which). I was in 12F (I think) exit row window. Arrived in PHX, walked out of the jetbridge and stepped aside to check my app for the next gate. Next gate was something like A26, looked down the concourse to the left and saw A28, looked to the right and saw A24, turned around and realized I had just walked out of A26. Boarded in about 15 min, into the exact same seat purely by chance although I usually prefer exit row window so the odds were in my favor.

Another time I was on the last flight of the day from DSM-PHX, which was my final destination that evening. We delayed pushing back about 30 min due to expected weather in PHX at the time of our arrival. They ended up opening the door and letting people get off who didn't want to risk missing their connection, but reminded us that many incoming flights would be delayed around the same timeframe so many connections could still be made. I didn't consider getting off since PHX was my destination, but wondered what I would've decided if I was headed on to FAT that evening as I often am. Out of curiosity I pulled up the app and checked the PHX-FAT flight, and sure enough the incoming plane for that flight was the one I was sitting on.