I learned a long time ago, never say what your own attitude was or how you acted. What you may think is calm and soft voiced can easily come across as harsh, rude, angry, frustrated, etc to someone else. OP even states they were frustrated on the phone. I can almost guarantee they were more upset and angry and frustrated sounding to the person on the other end than they think they were. I have personally witnessed people getting very angry and then saying why did they do that? I was perfectly calm and did not raise my voice, when they get shut down, hung up on, etc. You know what your intent is but you don't always come across as you think you do.

Just like in manufacturing, you can never do quality assurance on your own work.

And to be on topic, it does sound like the problems are Zurich and Turkish Air, Not UA. But it is hard to tell, there is not much of the actual facts presented. Other than mentioning the Turkish flight, I can't tell who operated the leg the luggage went missing on? There is too much missing info.