If you are getting graded material returned throughout the term, you should be able to establish a passing grade if not a totally accurate letter grade. My granddaughter had this problem one time. There was a substantial discrepancy between her final grade and what she had been receiving as feedback. I told her she should have met with the instructor with her evidence, a written record and copies of assignments with the grade shown. She said she did not have that. I looked at her and said it is your own fault because you know I advised you to keep a written record of your grades. To this day she won't do that, I guess the urge to blow off good advice is too strong.
My program dropped people throughout as is the usual procedure. Big secret at the end is not normal, however we did have an instructor with issues who enjoyed telling people at the end of the term that she had failed them so they could not graduate. According to her she was tasked with this honor by the program administration, so in some instances there is no honor amongst thieves. I am sure somehow this individual had some kind of paper trail, although everyone who failed, (anecdotally) to a student, maintained that she blindsided them.