I agree with some of the other posters on this. Although the deal probably could have been handled better, the seller doesn't owe an explanation here, nor does it sound like there was malice, especially under the unusal circumstances here with the previous owner.
Wires do get crossed sometimes when you have a scenario where two or more people are inquiring about trying to buy a cue. You live and learn. As a buyer, I have lost out on many a similar buy because I was stuck on the price that I thought I wanted it for....only to then see it sell for $50 or $100 more. And you know what, almost every time I realized later....I was dumb for not paying that little bit of extra money for it.
With experience, you'll learn to pull the pull the trigger faster. After all, that was a sweet deal on this fancy model Schon.....$800 or $750....both were a great deal.