I'm sure every state is different, but regardless of the law with just a verbal agreement how could any court even consider it, without at least an impartial witness like Bird mentioned.
Otherwise it would just be a he said she said affair how could any judge make a decision on those "facts" except to make no decision, maybe if you had receipts for specific parts or had pictures of his tractor in your yard you'd have a chance in a civil action but I wouldn't risk loosing more money on that.
Like you said, lesson learned. I guess I have yet to learn my lesson, I'm a state registered home improvement contractor, we are required to provide a contract for any work by the governing body, dept of consumer protection. It's mostly geared to protect the consumer, but could be helpful for the contractor if a dispute came up. I tell customers any contract I write is going to protect me more than them.
I often work with out a contract, I know if I finished a job and they refused to pay me I'd have no way of collecting, besides asking nicely. In 26 years of being in business I've yet to be sued or had to sue anyone to get paid, I've found that for myself I work better with trust than contract, not recommending this to others but that's what works for me.
On the subject, I just gave a lady a quote of $5,200. yesterday for a basement drainage system, she agreed so I asked her if she wanted a contract and she said she didn't care, what ever I decided. I told her lets both think about it for a couple days and if either decides for one we'll do it. In this case I may opt for signed contract as that's around the dollar amount I start getting a little nervous about.
JB.