Have you experienced discrimination in your civilian job for being a Reservist (despite it being against Federal and most State laws)?

I have been in the Army National Guard for the past 18 years and at my current civilian job for about 11 years. In the last few years, I have experienced what I believe to be discrimination based on job assignments and promotability due to the fact that I was away on a military deployment and various (shorter) military assignments over the years. Since then, I have watched other less-qualified people get assignments and promotion points over me, and despite continued requests, I am kept where I am and where I have been for the past 11 years... A supervisor told me "off the record" that it was because administration doesn't know when I might leave again due to my military obligations. This seems to be a clear violation of the Uniformed Services Employment and Reemployment Rights Act (USERRA) in addition to the California Military and Veterans Code. However, I have no proof. Beyond going to my union, I am not sure what my options might be...