@Ian *******
actually, TWO factors STRONGLY indicate that his visit was not rated a 90-days report:
*** the due date is on February 1, exactly 90 days after his entry. By December 24, this is still 38 days away.
You cannot do a 90 days report unless there are 15 days or less left until the due date (and until 7 days after due date)
*** the second factor is the missing slip. If he wasn’t given the slip into the passport with a newly stamped 90-days report next due date, he simply hadn’t done a 90-days report by December 24
It’s very EASY to understand, you just need to know the reporting process and simply understand what Immigration is doing. As a visa-advice reader since 25 years, I have understood the guidelines in use on Immigration offices