Is it okay to notice someone is trans?

I was at a concert and immediately suspected the guitarist was a trans. As the concert went on, it became more and more obvious as I noticed she had colorful dyed hair and was wearing a band t-shirt and her eyeliner was done transgenderly. I was so excited to see a real life trans in the wild like an exotic animal. So after the show I asked for her autograph. When I talked to her, she mumbled back to me in what was definitely a male voice. After she wrote the autograph, I noticed she'd written a male name so I asked her if she was trans. She admitted that she'd written her deadname so I insisted she write her real name and it was totally a stereotypical trans name.