A student in my ph d cohort got pinched for plagiarizing unintentionally and it was pretty serious, but eventually forgiven (she self-plagiarized from an article she’d written in a diff language, didn’t know she couldn’t do that). Also remember a University president in our system who was forced to resign for plagiarizing parts of his dissertation, which had been written 30 yrs prior. Also had a colleague who was reviewing a student’s final research paper, thinking “hey this kid knocked it out of the park” until he realized he was reading a plagiarized version of something he himself had written 15 years earlier (the student didn’t bother to notice his prof wrote the article he copied). Happens more than you’d think although I didn’t see it much at the graduate level that was intentional; usually it’s because of sloppy notes or ignorance of what constitutes dishonesty (e.g. self plagiarism). Sounds like the person who ripped you off was just completely brazen. Hope he gets filtered out before finishing and I’m glad it was cleared up for you.