Office bathroom break issue

Background: I work at a major hospital in New York State. Sorry if this sounds too farfetched or if the grammar is off. Long-time lurker. The true story: At work there was a several month problem where I was told to pee in a pee bottle when I couldn't be relieved by the department covering for me. One day a random visitor walked by my department (second shifters are alone after 5 pm). I needed to go to the bathroom but was told that I would receive no coverage. I had to use a bottle in the closet. I exited zipping myself up when the person saw me. I engaged in subterfuge for I wished not to answer her question of what I was doing. I was brought in to my bosses office a few days later and was given a dress code violation. I asked for a union rep and the rep didn't say a word on my behalf. HR made sure that people were trained to take over for me. No resolution was made rectifying this situation, beyond that. What do I do and who do I contact?