This is exactly what happened here:
> According to Valeo's complaint, Mohammad Moniruzzaman, an engineer for NVIDIA who used to work for its company, had mistakenly showed its source code files on his computer as he was sharing his screen during a meeting with both firms in 2022
In most cases, these people are asked to remove all such code from the codebase and never do it again, but news about this rarely reaches the executive level. Usually, there aren't clear rules that it's supposed to be reported, so low level managers handle it the best they can. Of course, this guy got caught in very unusual circumstances.
It is also very unfortunate to be the software engineer who notices others doing this, because it puts you in a whistleblower's dilemma. The upper management does not want to be implicated in this and they do not want to know. Besides, informing them would definitely lead to the coder's firing. What is worse, many programmers see liberal use of IP as "not a big deal". So you would be perceived as causing problems for upper management, and getting people fired for "petty" reasons. It can sink your career in most companies if you witness this and it gets out. There are laws that protect whistleblowers from being let go sometimes, but it's not conducive to anyone's career growth to remain in the company because they cannot be fired.