When Zenimax's lawyers talk about all this stolen "IP" they aren't pointing to specific code that was stolen. The entire case revolves around this idea that the Rift couldn't have been developed without Carmack and they own everything in Carmack's head. This is a hallmark of a claim that has no evidence and it's backed up by their claim of destruction of evidence which means they didn't find any stolen information during discovery (so of course it must have been destroyed). Such claims usually precede the case being dismissed for lack of evidence. Facebook's lawyers will likely move for dismissal for lack of evidence within days.
The first rule when looking at any legal case isn't to look at what the lawyers are arguing exclusively but to also look at what they are not arguing. They lawyers haven't listed a single line of code stolen and backed up by discovery, their claims lack any specificity and revolve solely around John having worked for them in the past (and claims that Palmer couldn't have developed this himself, claims with no evidence) and at this point in the case the lack of specificity is a death note for the case. All the Facebook lawyers need to do is stand in front of the Jury and ask where is the evidence of all these fantastic claims because there isn't any or Zenimax wouldn't be making the destruction of evidence claim.
In case you aren't aware a successful destruction of evidence claim allows the Judge to instruct the Jury that they should assume a lack of evidence should be inferred to be in the plaintiff's favor with the Jury taking the plaintiff's claims at face value. But you can't win a destruction of evidence claim without evidence of the destruction. Something they haven't demonstrated. These claims are almost always a hail mary to try to win a case where there isn't any evidence and the plaintiff is sure to lose without such a finding.