There are very strict "unclaimed property" laws. I used to manage the unclaimed checks for a very large global company. Payroll, accounts payable, travel, anything we might have cut a check for. States have different times for when such property is considered unclaimed. If memory serves, the average was about 7 years, but some were as low as 2 years. And this company had a manufacturing plant, or at least several salesman, in every state. And all I handled were un-cashed checks. Maybe that's why I do everything electronically now. Different rules apply to electronic payments.
But yes, there could be money out there for anyone that they don't know about. Thanks for posting! And congrats on your find! You gonna share it too?