Playing Powerball this week? Take care to check your ticket - you could be the million-dollar winner who will never know they won.

More than 300 prizes worth $1 million or more went unclaimed in 2013, the most recent year for which data is available, according to app developer Brett Jacobson. 

So he did something about it.

He developed an app called Lotto Lotto that alerts lottery players if they have a winning ticket. As part of the research to create the app, Jacobson requested lottery collection data from all of the state lottery commissions nationwide.

There actually tend to be more unclaimed prizes associated with a massive drawing like the Feb 2015 $450 million Powerball prize. 

That's because when people hear that they didn't hit the jackpot, they often neglect to check whether they won any smaller prizes, said Jacobson. "People don't even realize there are secondary prizes," he said.

About $2 billion in lottery prizes go unclaimed every year. Many of those are only worth between $1 and $5, but some players never realize that they may have a life-changing prize in their pocket.