Newsrooms that lived through the Watergate era settled on a rule that still holds, a claim needs more than one source before it gets treated as fact, and a sensitive one needs at least two or three, independent of each other.
Why one source is not enough
A single account, however trusted the person giving it, only confirms that they believe what they are telling you. It does not confirm that what they are telling you is correct. The point of a second and third source is not to catch someone lying, most of the time nobody is, it is that memory, incentive, and vantage point all distort accounts in small ways, and the differences between two honest versions of the same event are often more informative than either version alone.
Where this applies at work
A single account of a meeting you were not in, a single read on why a decision was made, a single version of who said what, all carry the same risk a single anonymous source would carry in a newsroom. Confirmed by everyone's silence is not confirmed, it is just unchallenged.
Where to start
Before treating an account of something you were not present for as settled, get one more independent read on it, from someone who was actually there and does not have the same stake in the story as your first source.
Where the two versions differ is usually more useful than where they agree.
Reading how much this specific situation actually calls for a second source, versus when one trusted account is genuinely enough, is a judgment only you can make based on what is riding on getting it right. What this gives you is the habit of checking before something with real stakes gets settled on one telling.
There is a specific way to ask a second person for their read without it looking like you are checking up on the first, and it is worth having in mind before the next account that matters.