I have a simular story, not about my children but about me. When I was about two, I had fallen asleep behind the curtains of our sliding glass door. Since I was asleep, I didn't wake to my mom calling for me, and of course the only place they never looked for me at was the one place I was. My mom called the police and fire dept. because I was missing - behind the curtains the police found me.
Although not funny while it was happening, we do get a good laugh out of it now.
My prayers go out to those families whose children aren't found so easily.