If you have multiple address books on your device (e.g. a "local" one only on the device and a "fruux" address book), iOS allows you to configure the default address book, where new contacts are saved. This setting is probably incorrect and should be changed to use "fruux" as your default address book account.
To configure fruux as the default address book account on your iPhone/iPad/iPod Touch, go through the following steps:
- Open the Settings app on your iOS device.
- Go to "Mail, Contacts, Calendars".
- Scroll down to the "Contacts" section.
- Tap "Default Account" and select fruux.