What to do if I lost my 1Password app or its data after upgrading my iOS devices?
iTunes has a bug in its iOS update process that can cause iOS apps (including, but not excluded to, 1Password) to lose all of their data. This bug can arise when either the app is updated or when the device itself has an operating system update, such as Apple's recent major release of iOS 5. It sounds like you have been affected by this.
Restore your data by syncing with 1Password on your Mac, PC, or another iOS device
If you have been syncing your data on your device with 1Password on another device, you should be able to recover your data by just resyncing. The details of how to do that depend on what sync method you have been using. Simply re-initiate the sync method that you were previously using.
Restore from a backup file created using 1Password's Backup & Restore service
If you haven't been syncing but you have made a backup using 1Password's Backup and Restore feature, then going through the restore procedures will allow you to restore from your last back up. Tap Settings > Data > Backup and Restore in 1Password on your device.
Try again with the iTunes restore
If neither of those two options are available to you, you might be able to recover your data from a backup made by iTunes. It is vital that you read the instructions below before you sync your device with iTunes again, because your next iTunes sync would remove the backup that you need.
For the details of these methods and, in particular, important instructions about the iTunes backup which you need to read before taking any further action, please see this document.
We understand how important your data is to you, and we do hope you're able to recover it. That's why we recommend that people make backups prior to any upgrade.