I highly recommend checking with your state's unclaimed property program as well as the national Missing Money site about once per year, especially if you've changed addresses frequently; and search for variations of your last name if it's commonly misspelled.
Since I have been a "permanent" resident of Texas, Florida and Michigan at one time or another, I check all three. A couple of years ago, my name popped up on Florida's unclaimed property site for an $80 overpayment I had apparently made to an apartment complex in 1999. Thanks to my previous career in TV news, I had probably moved two or three times by the time the complex tried to send a refund. So eventually the money was turned over the state.
I didn't think I had much of a chance of getting the money back because in addition to proving my identity, the state of Florida also required documentation to prove that I had lived at the apartment complex. I don't know about you, but I certainly don't have records that go back that far. I even contacted the apartment complex (via email like a good introvert), but the management said they only keep records for three years.
But if this happens to you, don't give up. Send the state as much info as you can find. Based on my proof of ID and promise that I really did live there, Florida sent me a check many months later. It probably helped that I have an uncommon name. If my name were "John Smith" then it may have been harder to prove.
Earlier this year, I searched the Texas unclaimed property site and discovered a bigger chunk of change with my wife's name on it. As most parents know, you get a zillion bills after you have a baby. Somehow or other, we overpaid a biller by about $400. Yikes.
We sent in the claim information and then forgot about it for a few months until a check arrived in the mail the other day. Of course, I'd rather not have overpaid anything in the first place. But these things happen.
Photo courtesy: sfgate.com