You may have found yourself in a very unfortunate trap. In order to get the funds refunded you need to file the return, 540NR. You will only get a refund if you file within 2 years of the tax payment. It looks to me like you may be out of luck if the money was taken 5 years ago.
I would suggest contacting the California taxpayers advocate to find out exactly what you rights are. If anyone can help you they can. The advocate hot line is: 1-800-883-5910.