Last year, I received a letter from a professor just as following: *** Graduate Advisor has given me your file for review. I am wondering whether you will be interested to do research in the field of ***, if I provide you some kind of fund. Please let me know. I received this offer and bought a air ticket to Mexico to change my visa. But unfortunately, this professor suddenly changed his mind and did not want to give me this offer. My air ticket is a non-refundable ticket and I can not get any m