Ask HN: Anything I can do about a probable confidentiality breach?

I had an idea that I emailed a payment processor to discuss about its integration. It was pretty radical. I got lots of questions so I had to describe it in an email but I asked them first to guarantee their confidentiality which they assured me.

After 3 months a company that is owned by the biggest stakeholder of this company launched the exact same idea.

Can I do something about it? I don't even live in US. I have all the conversation in the emails of course.