FLUKE

[noun] [C usually singular] [informal] - something good that has happened that is the result of chance instead of skill or planningI didn't even see which way I kicked the ball and it was just a fluke that it went in the net.It was a complete fluke that we just happened to be in the same place at the same time.By some amazing fluke the essay that I was required to write in the exam was one that I'd already done at home.