"Concepts" or "ideas" aren't really copyrightable. At least not in the US, I'm not sure where you're located.
"Boy meets girl, boy loses girl, boy finds girl again, etc." is a concept that's been around forever and will continue so. Most "original" concepts aren't that original, they just have a new spin on them.
Unless your piece is 99% exactly the same as the other piece, I wouldn't sweat it. If anything you might be able to use the other project to do a few new things with your piece. Also, you say you haven't written your piece yet, just the "concept" is the same. Again, I wouldn't worry about it.
I would, however, once your piece is complete legally copyright it with your government copyright office. I know a lot of people will tell you it's copyrighted legally as soon as you finish it and you can track it's first use. But, to save the time and effort, just pop the $$ to officially copyright it. (this is info from my attorney who IS a copyright attorney).
Write hard, write true.
