Haunted Blackberry or haunted piano?

I was on the phone with a certain someone late last night. We were talking about things and updating ourselves with progresses and the usuals. Usually, my friend will tell me in advance if the phone's battery is going off pretty soon, and that we will be cut off. But last night, maybe I didn't hear those words while I was switching from one ear to the other. But I thought I heard my friend told me to hold on for awhile. Then, out of no where, I heard someone playing the piano. A finger excercise piece that I recognize very well as I do that often when I want to start playing the piano. To my mind, maybe my friend wanted to show me that now my friend is able to play the piano. So, I let the tunes go into my head for about 3 reps of the excercise. Then, I started calling my friend, but there was no answer. So, I decided to put off the line and call back. When I did, the operator said that the number was not reachable.

I was like: "What the hell just happened?"

Usually, when the phone got cut off because of a dead battery, the line just mutes off. But the piano piece that i heard, I was sure that it sounded like someone was really playing it at the moment. And I am far more than certain that where my friend is at, there is no piano in the building. None at all.

Seriously, what did happen? I am 150% sure that I heard the piano playing and I wasn't imagining things.