stroke of luck
An unexpected fortunate occurrence. Meeting my favorite celebrity at the airport was certainly a stroke of luck that wouldn't have happened if I'd arrived five minutes later. I worked very hard on the script, but getting to pitch it to the producer in the elevator was just a stroke of luck.
a stroke of luck
Fig. a bit of luck; a lucky happening. I had a stroke of luck and found Tom at home when I called. He's not usually there. Unless I have a stroke of luck, I'm not going to finish this report by tomorrow.
stroke of luck (or good luck)
a fortunate occurrence that could not have been predicted or expected.