It's a long story, but I am still in the process of pursuing it legally. When I first learned of the acquisition, I didn't have the resources to pursue it, and even today don't have millions sitting around to pay attorneys. I sent a letter to the acquiring company explaining the situation and demanding that I receive my cut, and they actually responded with an extortionate threat in writing. We are now pursuing a civil federal extortion case against both the acquirer and my cofounder.
But, as of this moment, despite my name being on the company's first and primary patent, having written all of its initial code, having envisioned the entire concept of the company myself, and even having named the company, I have seen exactly $0 from an acquisition I was supposed to receive 20% of. Even better, with $60 million in his pocket, my womanizing, alcoholic, conniving cofounder suddenly found Jesus and now fancies himself a televangelist of sorts. At last contact with him, he was "praying for me". Go figure.
So yeah, be careful when working with others. My cofounder would have been considered by anyone that looked at him to be beyond reproach. He was not.