I tried using an old savegame. It would still end up disappearing.
Thanks for the tip about deleting scriptcache. I found a post about that some time after my post, and tried it. It worked fine.

Hi,

I have Sims 3 + ambitions. The Kama Sutra skill disappeared from all my sims after a save and restart at some point. I can't get it back. Any idea?
Please let me know if you need more info and what would be needed.
Thanks