Hi Geoff,
You may have a tough time defending this chargeback due to the amount of time lapsed, but if you supply all the information available regarding order details you may have a good chance of winning the claim.
To find your shipment in shipstation, go to the Shipments tab, then use the filter option to create a custom date range for the needed dates you believe this order shipped. I've included an example screenshot for visual aid.

You may notice that our customer information is now missing; Amazon removes customer information after 90 days, leaving us with only the tracking number and order number. Unfortunately, most carriers reuse tracking numbers after 120 days, so you may not be able to confirm delivery with the saved information. If the customer information is now missing, you can download a copy of the shipping label to confirm the customer's name and address.
As for saving your order details in PayPal, I'm afraid I don't have any advice for you. What selling platform are you using?