A vibrating what now?

So, I have a phone. It's on manner mode 98% of the time. This means that it doesn't ring, it vibrates ('cause that's how I roll). My phone was in my pocket. Someone called me. Now, taking that the phone is in vibrate, most people would assume I felt it going off so that is how I knew to answer it. Those people are wrong. Very wrong. I heard it go off. Once more; I heard go off. I didn't feel it at all, I heard it going off in my pocket. I don't think it's the fault of my jeans, but something is messed up here. I would like to think it isn't me.