SCAMMED by PPH Seller

Hello

As the title suggests, I have been hugely scammed by one of your clients. 
I am not even sure if he is in the right mental state, if you look at the job which is still open, you can see the very first few messages he accuses me of sending a virus. All i did was send him the work of a previous employee, after being paranoid and exchanges messages he then realized that he made a mistake. He then took on the project. Now i clearly stated funds will be released at the END of the job. He however kept pushing me, telling me he has no money to eat and needs it to pay some bills and get by. So as a gesture of good WILL i paid him,. twice!, Once for the deposit and once a little later, i believe the total i paid so far was around $350 . He then started to get al little quite, and pretend to be working on my project, but as the weeks went past i saw nothing change or anything new. Since i am not a programmer or tech minded he was manipulating me, showing me things and using tech language to try and act as if he is working hard, but when i said can i see something or what is the update, he had no reply. 
Anyhow, to cut the story short, because it is a long story, he has now taken my money and basically not given me anything. I am basically the same as a I started but 2 months wasted and $350 poorer! This is the behaviors from one of your most ranked freelancers? I am absolutely disgusted and i would like my money back, please advise me on what to do, he is now unresponsive. How can i get a refund? I am still due to leave feedback but have not left it yet and i am so glad i didn't leave it after i paid him, as he advised. 

In summary, i would like my money, he basically used your website to simply steal $350 for me. My project terms were clearly stated, all funds released at the end once completed. He manipulated me and used your site as a service to scam me. Last few messages we exchanged he was extremely paranoid, this explains why at the beginning he was thinking im sending a virus? I really do not think this person is fit enough to work with people.