The company that used to handle my mother's retirement account noticed that they owed her a small but not insignificant pile of money. One of the nice things about my having bought my parent's old house is that stuff like this where the error is old enough (most of the money owed is interest on their initial mistake) that the company wouldn't have gotten an updated address, I can just make sure she gets the check. Had she sold it to someone else, who knows if she'd ever see that.