Sure he has a case to bitch. They said they would hold the boat for him. They didn't.
THIS...all they had to do was call and say someone is interested, you are first option. At that point they would/should ask you to come with a deposit to continue to hold..
Your post is fine, nothing wrong with that being the reason they did not sell it to the other guy...with that being said, I really don't believe the other guy was ready....I can't see them turning down money in hand hoping you come back.
Congrats on the boat?!
ps....always put a deposit down on something you really want...it's just more binding that way.