Sims 2 legacy: sims disappearing

Hi,

I started playing sims 2 legacy with a female student for a few hours. The next day I am starting up the sims and the student is nowhere to be found anymore!

Then I changed to a female person starting up a big family, she had 6 children and it worked fine for days. Today I started it again and 1 of my children (the second youngest) disappeared. It is not in the household, not in the family tree, no recollection.

Disappearing sims is one of the worst bugs that can happen.