I work as a post-doc and do 1-2 hours of tutoring each week (approved by the university), to keep on top on my mathematical and pedagogical skills. Usually, students pay me after each session, but one of my recent students did not pay me the first, or even second session. After that, I have not managed to get in touch with the student again (via email).
Of course, something could have happened, but I believe I am being cheated. What is proper action here? Should I contact the professor for the course, or perhaps the students main department? Or just forget about it?