So here is the story:

I email company A asking for a specific service they provide. They tell me to describe my idea and I ask explicitly for confidentiality (but not NDA just expressed). 

Company A is in USA, California. 

They have an internal discussion and they decide that they do not want to provide me with the service because they are not sure if their investors/partners would be happy with it (very vague explanation).

After 3 months, company B launches an effective replica of the core of my idea. Company B is owned by people that are investors in company A. Company B's product now uses the service that was denied to me by company A.
Company B is sold for a 9 figure amount one year after to a much bigger company.

Do I have a case?