Happened to me once. Made a deal to buy a Z31 two seater (rare to find one in Aus), shook hands, went home, was going to pick it up on the weekend and bring cash. Get a call from the seller, he's been offered $500 more from a guy over east, and if I want it, i'd need to beat the other guys price by another $500. He kept saying I need the money for my family, have to think of them first, should have left a deposit, blah blah blah. Maybe I'm too old school, but you shake hands on a verbal deal it's as good as done. You don't welch out of it because someone offers you a little extra cash. I also knew he got the car from a wrecker cheap, and was telling me lies about getting it from a mate.
He was probably bull-shitting the other guy for more money too.