Why is it that my first statement always returns false when I make up a code that doesn't exist in the "Courses" collection?

// POST /api/my/courses
app.post('/api/my/courses', function(req, res) {
  let courseCode = req.body.courseCode.toUpperCase();
  let status = req.body.status;

  if (!Courses.findOne({ courseCode })) {
    res.status(404).send({ "message": "Course not found." })
  } else {
    let course = new MyCourses({
      courseCode: courseCode,
      status: status
    });

    course.save(function(err) {
      if(err) return console.error(err);
    });

    res.status(201).send({ "message": "New course added." });
  }
});