Only time I lost my kid was at home, I was in the garden, kid in the sandbox, 3 yeas old. I look up, no kid. My GSD, great historical protector of the family, was right next to me, looking for attention.
I freaked out a little, searched for 5 minutes, I have great line of sight, so covered a lot of ground. I finally found the kid, she had let herself back inside and was sitting in the good chair watching Dora, sand and all.
I public I get evil stares because I'll let the kid get about 15 yards away without hovering over her. I don't have the heart to tell the old biddies that closely watched and within pistol shot is my personal standard.