When you withdraw a student individually, there is an informative warning to make the drop date after the end of the semester or else the courses for the semester will be dropped. There does not appear to be a similar warning when you are in Users/Manage Student Enrollment and promoting, graduating, and withdrawing students at the end of the semester en masse. So the classes for 19 students were dropped and disappeared from their transcripts, etc. Fortunately, I have been informed on how to get this information back but a warning would have prevented it from happening in the first place.