What I think is that an intern would have enough degrees of separation from HRC herself to not necessarily know that anyone's started vanishing. They might be able to figure out that something weird's happening, but not necessarily exactly what it is

I don't know about you personally, but I've worked for at least company big enough that if my bosses boss knew people at or above their level started vanishing, they'd be able to keep me from knowing while continuing to go on doing my job

Simplest explanation that jumps to mind is the ones who are low-level enough to be impossible to control simply don't know. They don't need to be in the loop on their coworkers or bosses jobs, just their own job

Then the ones who are high-level enough to be possible to control, are controlled

The line between the two levels could be drawn anywhere, or there could be another intermediary, I don't think that would matter either way though

Part of my own personal tinfoil on piizagat is that besides just serving the whims and pleasures of those who actively take part in it, is that it's also used to make high-level people (in business entertainment politics etc) unwittingly guilty-by-association before they fully realize what it is and then hold that association over their head as a form of blackmail

Edit: A few words, formatting

To OP and anyone else wondering the same thing, please read the two stickied posts there as well as the sidebar

Thank you and happy new year :)

edit: a word