I am sorry to hear that you suffered this. You should have given him an idea, concept or generic example of your idea, like hanashivoice said below. You should never have done the work in advance and let him see it. Were you communicating with him through the message page? You should have directed him to the order page ASAP, and began to communicate from there.
I had a customer who pleaded with me to show her the names that I had in mind for her new business. I told her that I could not do that because I had no way of ensuring that she would not use them anyway, after saying that she did not like them. She whined that she did not want to spend money for names that she did not like. I explained to her that she was paying for my effort to create names. I gave her a description of the type of names I had in mind. I was not going to give her any of my names without her placing the gig order first. I told her that I wanted to help her since she said she was not having any luck getting what she wanted through buyer requests. I said that I needed more time than 24 hrs. So after a little more discussion she ordered the gig.
I ended up making her very happy with the names that I created for her. If I had not stood my ground by refusing to give her actual work in advance, I probably would not have her gig order under my belt now, and I would not have her enthusiastic feedback in my account.