What can you do if you suspect a company has stolen a concept from the work you sent in an application to them.

Say if you send a portfolio to a company. You don't hear anything back, then months later they have released a design that is way too similar / stealing the whole concept of the design that was in your portfolio. I think this has happened to me. What can you do about it? Has it happened to anyone else? I'm guessing nothing. But the feeling does suck and makes me mad. I've heard multiple stories about this happening to other people but the companies always get away with it because they have too much power, a