It is possible for your save game to be erased because of a factory reset or data corruption.
You can guard against these types of accidents by using the Cloud Save feature.
If your data was lost and you WERE using the cloud save, you should be able to sign in again on the main title screen or on the Event Details screen before a race, and you'll be prompted to recover your progress (chose the "Cloud" option.)
If your data was lost and you WERE NOT using the cloud save feature, then your save game is probably lost.  However,  if you made any in-app purchases, send us the order numbers and we can help you recover those items.