My research paper has been stolen on pretext of a book publication deal? What can I do? I submitted my paper to a supposed editor for publication in a book.
He never responded to the emails post my submission of the paper and upon contacting others from the mailing list I found out that they haven't received any response from him either.

A senior scholar suggested that I should partially publish the paper I sent so that I can save it from him stealing it. I did that and thought to forget it, but I just found out the supposed editor has a paper with my research idea in his list of publications. 
This person is now doing his postdoctoral research at a European university.

As a young scholar, I am feeling quite helpless.  What can I do in this regard? Please help me.

EDIT: So upon reading the paper I can see that he lifted my idea and sources and tweaked it, my research paper was a literary analysis and he has copied my methodology and core text along with my sources.
This is an unfortunate situation. I would try to contact that person's current supervisor (if you can find out who) and explain all this, and maybe s/he can reprimand this person. Additionally, I would also contact the editor of the journal and explain the same to him/her. It might result in the paper retraction on grounds of plagiarism/academic dishonesty. However, I am not sure how would you be credited for the stolen work. Maybe an addendum saying it was your idea or maybe publishing it separately altogether.

Edit1: As @CaptainEmacs pointed out, "Add email date evidence. It is not perfect, but at least corroborates the dates."

Edit2: As @ASimpleAlgorithm pointed out, "Presumably there would be vastly more evidence possible in terms of prior revisions and incremental experimental or theoretical work. It only takes a very short conversation before it becomes obvious which person is the plagiarizer and which is the author."