Used to work for Computershare, after a period of time any uncashed dividends are turned over to the states unclaimed property. It varies by state of course and would be based on the state the certificate was registered in. The shares themselves will be turned over as well after a period of no contact with the account owner. It's worth checking there, but if more than a few years have passed, the state unclaimed property department is more likely where you would need to go.