This is likely because you didn't enter them under a gmail account. This is necessary to keep your contacts synced at all times. If this is the case, follow the instructions posted on our blog here: 2 Guys 1 Droid under the post that is about keeping your contacts from disappearing. You are going to have to re-enter all of your contacts into your phone in the way that we have outlined there on our blog. For future reference, I suggest backing up all of your files using one of the backup apps. If you have any more problems shoot us a private message or email us at [email protected]. We have fixed this problem many times before so follow our intstructions and it should solve your problem. Enjoy!