Wow, never heard of the kidnapping in sims3, only in sims2. Will have to read about that one.
I googled kidnapping in the sims3, it did have a link, but when I clicked on it, it said page no longer existed. The other link I clicked on, took me to a story on the sims3 site, so I have not been able to find anything as of yet. Just have never heard of kidnapping after all of this time playing the sims3. Most of this invisible sims problems basically just started a couple of months ago, I could be wrong, but I really had not heard of too much before that.
If that is where you found the missing baby, there is not too much more explanation needed, just can't find anything on it where it has happened before.