Have you heard of silent data coruption?
Apparently, you don't.
There are many cases of silent data coruption that can appen, and none will cause ANY error message whatsoever.
You may have cross linked files. Most crosslinked files end up been truncated.
You may have truncated files.
You may have files with a missing sector in it's middle.
You may have some switched bits anywhere in a file.
You say that "The one thing that will NEVER happen is a hard drive reading a file back differently than what was originally recorded and not KNOWING that it was at least possibly different."
Well, it does appens, and much more frequently that you can imagine.
Another thing that CAN appen is that the file is not WRITEN as it was sent to the drive.