NAH. You have a disability, and you tried to do what you could to power through the performance. Unfortunately, the disability that you have prevents you from realizing the director's vision for the play. In an ideal world, you would have worked something out ahead of time (like maybe having the understudy fill in or popping a mask on for that scene), but unfortunatetly that didn't happen. You tried your best to play your part, and the director is trying his best to realize his vision. As a result of this event, the director has decided that his vision will be better realized with the understudy. That's how it goes sometimes. Better luck next show. If I were in your place, I would make a point of communicating my disability at casting time to prevent stuff like this from happening.