I think a "reasonable person" would believe it's ok to download the file, but then discard it once they realize the contents are not actually public. By analog

I think a "reasonable person" would believe it's ok to download the file, but then discard it once they realize the contents are not actually public. By analogy, suppose you receive a letter in the mail; you reasonably believe the contents are yours, so you open it. Oops, it was actually mailed to you in error; the contents belong to another person. Obviously you did not commit a crime, but you are obligated now to discard the contents.