It doesn't look like the auctioneer had anything to do with switching the bones.
Dean called the auctioneer but reached only his answering machine.
After a nod of her head, Paulette's hand shot up and the auctioneer all but cheered as he looked about for another sucker, his voice sounding like an old Lucky Strike commercial.
As an itinerant auctioneer he became well acquainted with the Germans in the S.E.
If the trunk didn't get switched while the auctioneer had it, then it must have been swapped back when it was in storage.
The auctioneer just removed them later, knowing no one would buy the junk if they could see what was inside.