Gotcha. My point was that normally, a cover-up job like this would be easy: Humans want so desperately to believe in finding mysterious and spooky hidden treasures that it would barely take any drugs to implant false memories.
However the event of the original unearthing was so traumatic and terrifying that the cover-up had to burn all of their memories of that day down (with high class amnestics) to the ground and start over from scratch. Hence the need for better mnestics to do the implant.
In my view the hallmarks of a good entry are: callousness towards humanity (casually having to erase memories), disregard for humanitys wish for order (cynically planting a dummy box because that's what they want to find), and feeling worse for having read the entry (knowledge that something *even worse* than something humans can imagine might be in a spooky box is loose). And of course, the banality and futility of the greater mission.