It's likely that TurboTax would have prompted you to review the Retirement Savings Contributions Credit section if you qualified for this credit. Note that this is a nonrefundable credit, so if your income tax liability is already zero without the credit, you get no credit. This credit cannot be used to reduce other taxes such as self-employment taxes or penalties for early distributions from retirement plans.
You can go through the process of amending to see if reviewing the Retirement Savings Contributions Credit section result in a credit and a refund and, if it does, file For 1040-X and Form 8880 to claim refund.
