Every year, people are losing money because they just don't know someone owes them. Earlier today, I saw something on NBC about a website called unclaimed.org which will direct you to the correct site for your state.
By law, businesses including banks, insurance companies, utilities, investment companies, are required to turn over inactive accounts to the applicable state after a dormancy period. In many states, the comptroller's office then serves as the custodian of this money until the person, person's heir or business comes to claim it. (Source: NBC News)
For Pennsylvania, where I live, the website was the state treasury and had a .gov domain. I searched my name and learned that I was owed a refund from Macy's. I have moved a few times in the past few years between college, my parent's house, and finally my own place so it's completely possible that I was owed a refund and they couldn't locate me. I filled the claim and we'll see if I get the refund and how much it's actually worth.
Update: I was asked about the legitimacy of this "found money" and I can't answer that with 100% certainty. As I mentioned, the Pennsylvania link is a .gov domain which according to Wikipedia:
To register a gov domain, a letter of authorization must be submitted to the GSA. For federal agencies, the authorization must be submitted by cabinet-level chief information officer (CIO). For state governments, authorization from the governor or state CIO is required. Domains for cities require authorization from the mayor or equivalent official; for counties, authorization may be submitted by county commissioners or equivalent officials, or by the highest-ranking county official.I hope this helps you decide if it's worth checking out.