I'm not sure what you should do now that the social worker is stuck. Try adopting another baby, maybe? Or move out and in in your house again (helped me when a police woman wouldn't leave).
To prevent it from happening again, don't greet the social worker before she rings the bell. It never happened to me, but I've read about it elsewhere on the web.

This once happened to me. If your kids are taken away, or become frozen, this will eventually wear off in about 24 hours, maybe less. then they just leave and the kids are under your control again. I'm guessing the social workers came because a parent died or something and the kids were left home alone.