CP59 Notice Received for 2021 Taxes - IRS Claims No Record Despite Already Receiving Refund

Just checked my account and got a notice saying I didnt file last year but I definitely did and even got my refund. The IRS sent me a letter from the Internal Revenue Service, United States Department of the Treasury in MEMPHIS, TN 37501-1498 with a tracking ID: 101566717987. The date of issue on the letter is 02-03-2022. The letter is addressed to me (KARL A GARC) and references Tax Period: December, 2021 for Return: 1040. The letter specifically states: "On February 02, 2022, we received a request for verification of non-filing of a tax return. As of the date of this letter, we have no record of a processed tax return for the tax period listed above." But this makes no sense because I filed my 2021 taxes and already received my refund! The letter says "If you have any questions, you can call 800-829-1040" but I wanted to check here first. Anyone else dealing with this? Should I be worried? What do I need to do to fix this? Do I need to send them proof that I filed? I don't understand why they're saying they have "no record of a processed tax return" when I definitely filed and got my money back.