I have never left/lost either of my DC. I did however lose my much younger sister (I was 14, she was 4) in a shop and had a complete and utter meltdown trying to find her.
That said, I have been known to have a heart attack and run around looking for DC/having announcements put out for them when I forget they wasn't actually even with me to begin with. I am that used to having them with me all the time, I always get that gut wrenching feeling when I see the empty seats in the back and think "Sheyat, I have left them!!" before realising that they are with their father/auntie/uncle/Nan on the odd occasion I actually get out for an hour without them.
It can be done. No, social services will not (and should not) get involved. It was a silly, stupid mistake but no one is perfect, including the PM/Queen/Obama and no doubt it will be a mistake that they will definitely try to make sure won't happen again.
It isn't like they had said "Oh, I have a brilliant idea. Let's go to the pub for a meal and leave DD behind for kidnappers", is it?