Forget it!

I don't think that you can get any remedies for this. First, it has nothing to do with copyright because only the expression can be copyrighted. Second, I don't think that your idea can be protected under the patent law because your idea might not fall within the subject matter of the patent protection. Third, I don't think it's a trade secret since it has nothing to do with a business and you failed to take any measures to protect it as a trade secret.

So the only way is to explore whether he has verbatim copied your work. If he is not, forget it. The Copyright law does not protect idea.