I was playing a competitive game and one of the enemy players kept saying my in game name. My in game name is hidden, I was not streaming, and none of my friends were in my game. How could they know this info?

i was q’ing with my friend and my friend was also stressing out that we suck but he give a bit of criticism meanwhile our pro sage was freaking out every time each of our teammate dies and keep blaming one of us. Its unrated, meant to be a...