Yes but you cannot tell exactly what happened without the light reaching you. Sure you can guess. For example, if you know the state of a star a few billion years ago, with no other information after that, you can calculate at what point it would become a supernova. But without the light reaching you, there is no way to tell whether it actually became a supernova or something else happened (eg - it got swallowed by a black hole etc.)
It might actually be useful to think of that as an equivalency because “c” is the fastest rate by which one part of the universe interacts with another part. I think of the universe branching off by the further in spacetime these interactions have to travel. The whackiest QM interactions are still bounded by “c.” The distances between events are called space-like precisely because light/etc would have to travel faster than light to go from A to B.
The person(s) you're talking too are not talking about epistemology. If something happened yesterday and I am not aware of it until I read the paper today, the thing still happened yesterday. If I never read about it, the thing still happened yesterday.
Whether/when I "know" about it is separate, and not what they're talking about.
I agree you can't tell what happened after a observing a recorded event. If you were to read someone's diary from a decade ago, you wouldn't know what they were doing now. You need new observations.
The OP was referring to when a event happened though.
It's like saying that when you see a dead body with a sawed-off head nobody knows whether that body was born this way or somebody is a psycho who decapitated it.
For the sake if the argument let's allow this body to be an light-hour away from us when it happened.
What I said in no way prevents us from guessing or inferring what could have happened using knowledge known to us. But they are all possibilities, some more likely than others - there is no way of knowing 100% which one of them actually happened without evidence or information in the form of light or radiation.
> But how do you know that it has taken place without the light reaching you?
Things happen without us knowing about it, and without light from such events ever reaching us. We don't need to know it has happened for it to have happened.