Here is my 2 cents on it. Seller tells in his last sentence to ask questions before bidding. Like stated, no body bid, so my quess is that this person was lurking and waiting for no bids and then approached seller and made an offer stating "since there were no bids on your item wouuld you take $$$$$ amount for it.
Seller gave a full description and it doesn't mention anything about a 3 day inspection in the listings.

"Beautiful .410 SxS for sale. 26" barrels, 3" chambers, IC/Mod, two triggers and extractors. Gun was bought new in March of 2007 by me. Still looks like new and is actually better than new, in that it has two ivory beads, manual safety and a .6" Pachmayr Decelerator pad and all the misses have been shot out. Comes in original box. Weighs 5 lbs. 7 oz., 14-1/4" LOP, DAC is 1-1/2", DAH is 2-5/8" and has 1/4" cast-off. 2008 price is $1995. MY PRICE INCLUDES SHIPPING AND INSURANCE TO YOUR FFL. Please ask any questions you may have before bidding."

If seller added 3 day inspection for item in an email, to me it would mean if the gun didn't fit or some unknown problem but not that the buyer didn't like the 26" barrels. It was there in black and white how long they were. Like stated I also believe that the buyer found another one with longer barrels and possibly cheaper.
So in my opinion, why would Jim accept the return? The deal was done out of Gunbroker and maybe that will teach the buyer to buy the item on the auction site and not to make a "deal" afterwards.

It's not a good thing to hear and read about, and I hope this is settled in an amicable way.

David