I have a hard time believing this is a simple “mistake.” At a large media organization like Fox News, they don’t just have a bunch of video clips laying around. Their clips are organized, labeled, and dated. They HAVE to be. When there are many editors working with the same material, organization is absolutely crucial or you’ll have complete chaos. I’m not familiar with Fox News’s procedures, but it wouldn’t surprise me at all if there’s also a version control system in place, where clips and media files need to be explicitly checked out for use in a particular project.

It’s MUCH more likely that this was deliberate.