I read through all of this too. It just seems that 1. why would the consignor decline? 2. if he did decline, especially "in writing", then why not post proof?

As you suggest, maybe the reason is more complicated, e.g. some was sold, consignor not happy to have what's left returned and no compensation for what was sold, so refused to just have the smaller amount of stuff returned. If so that could have been much more clearly expressed in this letter. And again they could just post the correspondance.

Difficult to imagine why it would be declined. Did they perhaps insist on unreasonable conditions for doing so, such as fully indemnifying them in the matter? (Just wild speculation on my part since for whatever reason neither party seems interested in providing a full, clear, objective telling of events.)