Removing any user record(s) in db is sorta taking a chance on 'orphaned' whatever - ditto for a course by id.
I know this is gonna sound strange, but, error is kinda strange ...
In admin/cli/ there is a backup.php script that can be used to backup a single course and that backup can be saved outside the 'sea' of files in /moodledata/filedir/. You know the course ID ... 1938
So let's see if there's anything tied to the course:
mkdir /path/to/moodleDATA/check
cd /path/to/moodlecode/admin/cli/
php backup.php --courseid=1938 --destination=/path/to/moodleDATA/check/
That might very well error out ... which, in this case is a good sign that the backup can't find stuff for that course.
**Might** need to inspect what Moodle was able to build for the backup ... in /path/to/moodleDATA/temp/backup/. There **might** be a moodle_backup.xml file or other .xml files and from them, **might** be able to see other things that are related and **might** need to be investigated.
If user had a teacher/manager/admin role there could be files associated to user ... and one really doesn't want to get and orphaned files situation/started with moodledata/fileir/ ... especially large backups.
As far as the user ... search mdl_users for that user ID ... which is actually the row ID.
Needless to say ... make a backup of the DB before ... just in case.
'spirit of sharing', Ken