We recently fixed an issue in Cliniko's patient details screen. If you imported patients that already had their "Referral Source" field filled in, this field wouldn't show up on their detail screens. This happened because these imported sources aren't associated with one of your account's referral source type.
There's no reason that the lack of this association should prevent the data from being displayed! From now on, the patient's imported referral source should always display on the patient's detail screen, where you can add its type at your convenience.