If your employer was the company, and not the owners personally ... Then you have no claim against the owner. You can try ... But I doubt if you will have any luck. That's why companies are incorporated, or limited ... It takes a lot of the personal responsibility and liability off of the owner.
This all depends with the prior agreement that you had with the company although I believe that you have a case. Nevertheless, I believe that you can try getting a lawyer so as to know if this can be done legally.