Shog
The Infinite Being
Off the top of my head, I'm thinking that KorTech got their hands on alien tech and wanted more and more as they managed to reverse engineer it. Eventually they reached out to the aliens themselves and reached an agreement of sorts: Powered people in exchange for technology. Both sides going into the agreement thinking that they're playing the other, but in the end it's a mutually beneficial relationship. Though the aliens don't particularly like that KorTech's trying to get their own powered human research department going using some tech that wasn't actually supposed to be shared (but was because one of aliens is trying to use KorTech for his own gain against his own people...).
What would be found in the files would be mostly... communications with the head office about the research programs looking into [name of alien race] Tech and communications about KorTech's own [name of superpowers research project] Project. Mostly in the way of orders about "finishing superhuman evaluations", name dropping Galeforce, Rocket, and others people who had been looking into the disappearances and the names of a few villians and heroes who they think they can get signed up as allies. Also sprinkle in concerns that the more people they take, that the more attention they're going to draw not just from superheroes but from everyone... and then the higher ups rebutt by saying-lets quote-that "Securing the Technological Superiority of Humanity supersedes everything and that the projects must continue for good or for ill and that future generations will applaud them for making the hard choices necessary in the realization of this goal." Of course completely leaving out the fact that-for the most part-the people running the show are actually just a greedy businessmen who want to control the entirety of Earth's supertech market (but let's throw in some insider guy that'll side with the heroes or try to get their support out of their 'duty to humanity' when things start looking grim).
Also the paper trail should lead to a KorTech regional office and/or one or more of their more secluded labs (so we have somewhere to go next).
I like most of this. Perhaps they only had a small amount of non-lethal tech they were using and the aliens made first contact. This makes more sense to me because they aliens would be somewhere other than earth and the people at KorTech wouldn't know how to contact them. The aliens, on the other hand, have the tech to make easy and descrete contact as well as the location of their missing tech.