And.. may I know, what happened to the third seller?
Don't consider your money flew away. Since it was the price you were willing to let it go in the first place anyway.

Furthermore it's only less than two weeks time since you sold your board. Givve the fella some time to reply to you. He can just tell you that the board isn't working, right? And don't need to pay you the 30ringgit, even when the board works at his side. It'll be up to his personal ethics then, unlucky for you.