How to deal with a delayed package from three years ago?

I got a message from a buyer saying their package is delayed and not delivered and they need a replacement or a refund. So I try to click on their order number to the right of the message, but it kept coming up as an error. Then I noticed that below it says the order was purchased in 2022. I was able to find him in my own record, but unfortunately I can’t find his tracking number or access his order on Amazon at all to find it. Hell, I’m not even sure it would show up in USPS at this point. So what should I do?