Boston University interview questions

At first, interview went quite smoothly. I applied online and had two rounds of interviews on Skype with the faculty. They offered me a job verbally and told me that I would receive the written job offer by email. However, after waiting for a couple of weeks, I heard nothing. When I chased it up, I was told that they offered the job to someone else. I do not have any problem with my application being refused, but this was a very unprofessional behaviour from the department. They refused to give me details about what happened. They played games with me.