I also had a cancelled flight win this weekend. My first flight was delayed, making it look doubtful I would make my connection. They protected seats for us on the first flight out the next morning. Delta ended up cancelling the first flight the next morning, and protected us on different flights. In the end, we made our connection, and did not need the flights they protected us on. The protected flights were still showing in the app after we got home, so my SO called Delta to let them know. They removed his, but mine still showed in the app. The next morning I got 10k miles for my cancelled flight...which I did not need since I made my connection.