Ahoy! EAMobile hopes that you didn’t update your iPhone / iPod Touch versions of The Sims 3 yet as there is a major bug – all your saved games will be lost! The Sims Team is investigating this issue but would like to inform you that if you see it available to update in the App Store, do NOT proceed to do so.
For those of us that already updated their game, there is no fix for us at this time. Hopefully EA can chime in what to do if you are one of the early victims of this patch.
Source: EAmobile Twitter