Goodwill Industries used to sells thing on ebay or even amazon. In the past, I have seen old books on Amazon in the used section. Once when looking on ebay for a specific piece of tupperware, I saw that Goodwill had some for sale on ebay. Certainly surprised me. Haven't shopped ebay in a while so don't know for sure. I guessed that when a donation is made, someone somewhere looks through it and determines value so those more valuable antique type things don't end up in the store selling for 2.00 when it could be worth hundreds or thousands. My guess is a handmade quilt would find its way to a third party site to be sold for more than a quilt would bring in a local store.
I wish the family much luck in locating it.