That does not implicitly declare that a test bank is okay to study from, since it says on it that it is not for students. Any student would question to themselves whether they should use it. So ethically speaking:

1) Ask the professor before the exam if it is okay to use the test bank. He will say, of course not! Why do you have it anyway, it's not made available to students - are you trying to cheat?!

2) Astonished that the test bank was the exam verbatim (though I'm sure few students were), students should have told the professor that many students used the test bank, not realizing he would pull the questions directly from it. Of course, no one would do this directly since students aren't supposed to have the test bank in the first place ...