Quiet Study Area

I take headphones to school and I listen to music (on the internet) while I study, or else my mind wanders and I end up listening and watching all the people that go by in whatever library or study room that I happen to be in. Today I was in a large computer lab studying (I had been in there for about 20 minutes) when a guy tapped me on the shoulder and asked me if I realized that my head phones were not plugged in all the way.... Meaning that while I was studying hard, trying not to disturb anyone, EVERYONE in the whole QUIET study room could hear my music the entire time. Why didn't someone tell me right away? Why did people just walk by smiling and say nothing? I was so embarrassed!