Who was fooled?

I was nursing Darcy in her room upstairs just before nap time, enjoying the rare peace and quiet without Drew and Mason fighting over the last inch of my lap to sit on, when I heard what sounded like a bat being hit against our sliding glass doors downstairs. The baby monitor was on so I said "Mason, knock it off," in my normal voice because I knew it would come through loud and clear downstairs on the receiver. I thought that was a good trick and it actually worked, no more noises. I was sure that I had just taught my kids that mommy is all knowing, all seeing, and they can't get away with anything, even when mommy isn't in the same room. A few minutes later I heard the usual sounds of fighting and screeching so I did it again, "Hey guys, knock it off, find something else to do besides annoying each other." I was giggling at what I thought their reactions would be to my disembodied voice. I finished up with Darcy and headed downstairs and there on the floor was the baby monitor receiver, turned off. I guess they knew exactly where my voice was coming from and they decide not to listen to me anymore. Now I wonder just who was fooled and who was doing the fooling.