Missing your mates

I've been stressing the importance of not missing checkmates in 1 to a couple of coaching groups I've been working with this week. The point I am (obviously) trying to make, is that once the game is over, your chances of losing fall dramatically. Of course I then saw a couple of games where the mate in 1 was overlooked!  In one instance the opponent went on to win, while in the other, a draw was agreed when both players ran short of time.
The diagram shows the second game. In this position Black thought for a while and then played 10 ... Ne7. White then committed the cardinal sin of playing the first move that came into his head and replied 11.Nxe7, missing 11.Nd6#