Yes, once on the https://prefunds.aa.com/refunds/ site, click "Request a Receipt" and enter your ticket number. If you don't know your ticket number (or you deleted the email containing it), the ticket number is usually on your credit card billing statement for the flight purchase.

I was able to retrieve a receipt from a trip in May, so hopefully it works for you.

More information here:
Print Itinerary and Receipt, & How do I find ticket number?