The thing that sticks out to me in Rybski's message is that, by his own language, he implies that he was wary of Chauncey as a customer from the very start with the "random checks" comment. If this was some sort of red flag to him, he should have taken better care to make sure Chauncey understood the process and the risks of proceeding with a "fly-by-the-seat-of-your-pants" approach BEFORE accepting the deposit.
It seems that Rybski entered into this with reservations about his customer...and didn't handle the situation well when Chauncey offered some resistance to his plans or suggestions. The thing about being in business is: To reap profits and prosper, It is the business's responsibility to make every customer happy.
If you are in a custom, specialty market such as Rybski Basses, you should back out the minute you feel that is not possible to please your customer. In this case, Rybski was happy to cash the checks and move forward with a customer he was obviously not comfortable with from the beginning. Rybski would have been much better off to send back the "random checks" and tell Chauncey "I am not the right builder for you."
So, at best, Rybski is guilty of neglecting his responsibility to his customer or...at worst, he manipulated his customer into forfeiting his deposit.