Hi and thanks for this practical question. It is a dilemma we did not consider--when you use stash stuff and no longer have actual receipts!
I would say that a copy of the item's listing and cost from a web site or catalog would suffice even if you no longer have your personal receipt. But a web shot or copy of a page must be provided, we can't simply be referred to a web site.
Good one, J! Thanks for asking.
Leslie, editor in chief, Step by Step Beads, Creative Jewelry and Bead Star