work product?

I just learned that someone outside our office may be taking over a juicy case of mine. I was ready to file a pretty significant, highly original, painstakingly researched, time intensively written document. The word came down that I have to give the document away and the outside person can use it as his own. I was told it was in the best interest in the client.
I was almost ready to finish the case up - I never figured it would end this way.