The people who issued your bonds or their transfer agents are the people who now have your cash. So I would contact them for instructions. (Read the fine print on the bonds carefully. You may find instructions, additional clues or the name of the transfer agent there.) Who mailed your interest checks? What bank issued the checks?

If all else fails, contact your local full service broker. For a price, I am sure they would be able to help you.

When you asked the bank, did you go to the Trust Department? Many banks no longer have trust departments, but they are the ones with the knowledge. Your bank should be able to recommend a local bank in your area that does have a trust department.