[ndl]

1) Many of the students probably received the test from their peers and did not know that it had come from a private test bank. I seriously doubt 200 people independently and individually broke into the same test bank, unless it was actually open to students, in which case it was as much fair game as the rest of the Internet. There are plenty of universities that keep student-accessible test banks and records of old exams (including the two I've attended), so many students probably assumed it was from that type of source.

1.5) Also note that the concept of a "test bank" that is supposedly inaccessible to students is not entirely common knowledge. We don't know how easily accessible and/or clearly warned this information was.

2) I already said that the students were wrong not to mention that they'd seen the test.