A student shows up on the report "Student without Reporting Attributes" but is not rostered in that term.
There is a test for that student in the current term. It is likely that the student was rostered, took a test, and then a user un-rostered the student by removing the term, or by importing a "replace" roster that did not include the student.
You may disregard the student. However, if you wish to remove the student from the report, take one of the following actions: