Memory Lane sold cards they didn't have per SCD

[Yoda]

Just a couple of insurance points; first, as this appears to be an inside job, who at BW signed for the package, where was the package stored after delivery and who, if any, was told that something important looking was now being held, second, if there are no visible signs of forcible entry or break-in, then any employees involved with the package would become immediate suspects. I assume the police have investigated all this already.
Most transit policies are covered by an inland marine floater cover, normally on an all risk basis, including theft. I somehow doubt that ML has high enough limits for cover, unless they arranged a higher limit for this dumb shipment.
If the insurance company pays and the cards are recovered, then they take possession of them. That is a standard clause in virtually all property policies.
If the cards are not recovered then the carrier will subrogate against BW due to their negligence. The small statutory innkeepers liability limit will not protect BW in this case.
It will be fascinating to see how it all plays out. Of course, I have to wonder if ML can survive all of this; a bad hit to their rep, financial considerations and disgusted consignors, some of whom may take judicial action against ML.