I managed to recover the lost data, upgrade, and sync. It took a while. I restored the backup twice.
In chronological order:
1. Upgrade OTA = data lost
2. Restore backup
3. Upgrade the eWallet only on iTunes
4. Sync iPhone = error "app eWalled was not synced...." = app updated on the iPhone but data lost
5. Restore backup
6. Sync iPhone = (eWallet already updated in iTunes - step.3)
After this I had the old data with the new eWallet.