Did you file your taxes in 2008? If not, the IRS might have $600 with your name on it. The IRS says  they have about a billion dollars of taxpayer dollars sitting in their coffers because people didn’t think to file their taxes that year. Half of them are for more than $600, because those people were eligible for the Recovery Rebate Credit .
There were a total of 111.7 million returns and with the average tax refund  in 2008 at $2,728, according to the IRS statistics , so if you didn’t file in 2008, you probably should just to see if you were owed a few dollars.
Incidentally, having only $1 billion in taxpayer dollars is less than the $1.1 billion they reported the year before, so we’re doing a little better. While you’re at it, see if you’re due any missing money . I checked recently and found a small paycheck back in college (sadly only worth like $20, which was a princely sum in college).