The drive may have been in plain view, but since the evidence is contained inside the drive in digital form that isn’t apparent without plugging the drive into a computer, then the evidence certainly was not in plain view.
They asked, he told them. Kind of like when the coppers ask what is under that blanket in the back seat and you say, it is a gun. They toss the blanket, find a gun, run the numbers and find it is stolen. They always take the gun.
Now on a search, one cannot go say looking for stolen gold bars in an apartment with a warrant for records of same. Gold bars in no way look like a sales receipt so blasting into walls or floors is not covered by a warrant for records. IMO of course.