<human>: I'm currently attending the University of South Florida, and this past spring I took a stats class that I passed with an even C. I really struggled with it, mostly because the instructor was terrible, but I need it for my major.

I checked my school's grade tracker over the summer and everything was fine. Fast forward to Sept. and the C is suddenly listed as a D+, which is bizarre because our learning management system, Canvas, still lists the final grade as passing. Whatever happened, it pulled my GPA down and needless to say I'm upset and worried.

I emailed my advisor asking what to do, and she said to contact the instructor. But here's the kicker: the instructor told our class that he planned to leave the university, and lo and behold, I can't find him in the school directory and his name isn't listed under his department. I couldn't find him in his previous university's directory, either. I told my advisor this, and it's been over a week since she told me she would be contacting the department manager. I figure I'll wait another week, but after that I want to start thinking of contacting someone else. I don't want to wait so long that it can't be fixed.

I mean, how often does this happen?! I do remember leaving a frankly honest instructor evaluation at the end of the semester. Maybe they aren't as confidential as I thought... Has anyone else had an experience like this? Who did you contact to get the grade resolved?

Summarize the given text in a few sentences.
<bot>: Final grade suddenly changed from passing to failing. Instructor since vanished. Advisor doesn't know what to do (yet). What should I do?