Investors have a large number of companies in their portfolios and new proposals all the time.
They don't want to open themselves up to a lawsuit should they later back a competing venture. Lawyers and accountants are privy to the secrets of many clients. If you push too hard on the point at this early stage, the financier or professional will simply pass. If your idea is patentable, patent it. Well, the truth is that somebody already has your idea, and your next one.