I was going to sublease a room for 2 months this summer. I paid it all upfront and within a week or two of my move in date I realized that it wasn't the right move for me. I called and told him that I could not move in and I wanted my money back. He returned half of the money. He left within a week to California and could not find another person to rent out the room for a month. He now claims that he will not return the other half of the money because of the month that he lost due to me backing out and his inability to find another subleaser. We did not sign a contract that it why I want to take him to court for the other half of the money. Do I have a case?

Its your fault. Unless you can prove he did not make a good faith effort to rent the unit, you signed a contract and he was nice in giving you back half the deposit.