Wendell,
When I run a report with the category "Schedule", operator ">", field "not seen in last X months" and value "250", I get a large number of patients (thousands).
Prior to starting with AC about 15 years ago, we scanned in all our old paper records. That means many of our patients who were never subsequently seen actually have some old records scanned into imported items.
Nonetheless, I would think this report would also include all the "registered but never seen" patients you are trying to identify.
Is that the same way you ran the report?