Once again I will repeat it. The Star Trek technology you are thinking about is far far too
expensive to be used on insignificantly small cases like somebody downloading something by
accident and immediately deleting it. There is no way in any circumstance that the most
expensive scanning tunnelling electron microscope technique is ever, under any circumstance,
going to be used on anything less than a national security matter, period, end of sentence.

If you're not spreading anthrax around D.C. or mailing a hard drive full of uranium enrichment
info to China, a military standard DOD 5220.22 secure wipe that most secure delete software
is capable of is more than sufficient to make it effectively impossible for the FBI to cope
with or afford.

They're still using AnaDisk, for crying out loud. Do you know how old that puppy is?

For the few that accidentally download something a simple delete followed by
defragging the drive is more than enough to put their minds at ease. To think
otherwise is to be superstitious and to tell people otherwise is sensationalism for
the sake of self entertainment.