Appstation UI Developer interview questions

"I attended an interview for the position of UI Developer and completed the machine test. After one month, they contacted me and issued an offer letter. After receiving the offer letter, I accepted it and resigned from my current job. However, two days later, they called me and informed me that the project they were expecting did not come through, so they are holding the offer. They mentioned that they would appoint me only if a new project comes in, and only after another technical interview. My question is, if they don't have any projects, why did they post a job vacancy in the first place? Because of their unethical work practices, I have lost my current job. I don't believe they have any work ethics at all. Be cautious of these kinds of fraudulent companies."