I think its a case of getting out sharked by an aggressive buyer rather than the seller being being a ______ . What the seller did wrong (and its not a small thing) was lead you to believe they were going to hold it but that's likley just stupidity around commercial stuff.
The OP is no doubt an honourable guy who behaves in an honourable fashion and expects to be treated as such. However the seller doesn't know that and, if his experience is like mine, conditioned to think 75% of inquirers are flakes. What probably would he give that someone is going to show up the next day? Even then it wasn't, that I could see, a firm deal i.e. still open to inspection.
Competing with a buyer that aggressive, imo the moves are either pass, get over there right away or e transfer the 1800 and message him "sold"
No offense intended, been on the losing end and been on the winning end. The losing end sucks.