In the Traveller scenario as you envision it, who decided there was a safe? Why does the dirt matter?
One superficial answer is that in 5e an Investigation check will confirm that.
But a less superficial answer is perhaps the following.
It might be these concerns come out of the way we talk about these game moments. We zoom in on one event, which pushes toward an all or nothing interpretation of that event. It leads to questions like the one you asked where the whole thing could be felt to turn on one decision. So it's important to clear up that it doesn't turn on one decision, because each is constrained and formed in light of what comes before it.
Going back to the concept of fictional positioning, we're in a negotiation where at some point everyone at the table nods and agrees that the accountant knows the location of the dirt. If someone says otherwise at this point, either they're about to introduce something everyone will nod and agree to (something everyone else forgot until now, or a breath-taking revelation of a new gestalt), or they're reaching (errant play or a spoilsport).
It's akin to a chain of open-ended skill challenges. At various nexuses the group has "agreed" resolution of a conflict hinges on the consequences of the course of resolutions up to there (a chain of moves in the fiction, checks and other game events.) Depending on the group's interest in pretend violence, every so many conflicts will step into combat for their resolution. The way we have spoken about the safe makes it sound like the last resolution in one such chain (likely we will play out the actual revelation of the dirt, and commence new chains - there can be multiple chains at any one time.)
The accountant knowing the location of the dirt emerges out multiple moves and events, and participants at the table have fluctuating levels of authority over each one. In that way, the accountant knowing the location of the dirt is a group determination. It wasn't reached in one jump - we're only here, running social interaction with this accountant, with this attitude in play, because of what multiple participants said up to now. It might have been that in this case the accountant entered the world as something a player imagined.
Frex, two sessions back, before the location of the dirt was at issue. Bob - "The kingpin has an accountant right?" and everyone nodded and so now we know there is an accountant. What Bob said was not just plausible, it was the right question to ask just then and followed from our situation and descriptions to that point. Everything we knew about the kingpin made it right to say "yes" they have an accountant.
What might the accountant know? Seems like one decision. It's not one decision.
Perhaps let's leave this here for now? It may be nothing turns on it. If it does, I'd need to see more of the text before I could agree (what you have quoted does not lead me to your interpretation.) And then even if we settled that, we'd still have a debate about what Social Interaction + Insight + Investigation permits players to do in 5e.
Possibly it's more fruiful to think about the chains of events that together can lead to group decisions (decisions that can't be attributed to one member of the group alone.)