I remember when I was about 10 my sister had a baby. As most new mothers do, they get one of those baby monitor devices so they can hear if there is any trouble and not have to be in the room with the child all the time. As it was only my sister and me home, we sat down to just relax and play around. Suddenly over the monitor a baby was crying and making little noises. We thought this was cute until we decided that it didn't quite sound like my nephew. So my sister went upstairs a bit and came back down, shrugging and looking confused. I asked her what was wrong and she told me that it wasn't her son making those noises. We kept checking but still, it wasn't her son. So we started to get a little concerned. Soon we got out a small tape recorder and put it up to the speaker, and recorded. After awhile the noises stopped and we went to listen to them again on the tape. BUT THERE WAS NOTHING THERE!!! To this day we still don't know where the baby noises were coming from and why they didn't record.
I guess it is just one of those things.