Having coached a number of students with this trait, it is often difficult to get them out of this habit. The obvious cure is putting them up against stronger players who do see the threats and then punishes the bad moves. However this 'cure' has a tendency to go to far, with a number of players losing interest in the game once the source of cheap wins dry up.
Nonetheless it may be possible to catch a stronger opponent off guard. While researching this article I found possibly the most audacious example of 'he might not see it' in a game between Gary Kasparov and actor Woody Harrelson. Harrelson decided to see if Kasparov had previously seen the "Four Move Checkmate" by starting with 1.e4, 2.Qh5 and 3.Bc4. It turns out Kasparov had (assuming he did not discover a defence independently) but Harrelson at least proved he had a few more arrows in his quiver. He played the rest of the game fairly sensibly, and with the position even, Kasparov decided a draw was the correct result!
Harrelson,Woody - Kasparov,Garry (2812) [C20]
Prague consultation Prague, 12.07.1999