Dan, I find your answers very honest,you admitted that Bob's offer was a better deal than what you asked for originally and you admitted selling before you had the book back so you could maximize your profit. I applaud you for that.
However you must see that your actions also have consequences. You sold a book before you had it in hand, and before you had the graders notes. You made a statement about a "stain" that turned out to be in error.
So, I think there are errors on both sides.
Bob's error was making an offer of a trade to begin with. This is why I don't love trades, i'd always have traders regret.
However, I can absolutely see where his offer of cash should have solved the problem, he was offering full asking price. You on the other hand saw a better deal and you wanted that. The fact that you later would have accepted the full price (after getting the book back) just further muddies the waters.
The end part, the part with the stain, well that's more on you.
I would really love to see you both just walk away and call it a day.
I don't see any other reasonable solution here.
Sharon,
I agree with the majority of what you wrote save for what I bolded above. I think it should be clarified that Dan HAD a better deal already agreed to (the cash/trade) and he wanted that adhered to.
That's what she said. Re-read it. Wait. I re-read it. She was correct but not about the timeline. my bad.
A bit confused by your edit
Perhaps I am splitting hairs here but I'm not sure I agree with the "offer of 16k cash should have solved the problem". By doing so it would have been accepting a less favourable deal than was originally agreed to by both parties. As I understand it, Dan wanted the original cash/trade deal adhered to and I find absolutely no fault in that. Could he have accepted the entire cash deal? Sure, but that is his prerogative as the seller, especially since a deal had already been finalized.