Bret Devereaux

Now, to be sure there is only one survivor, but his account reaches Rivendell and find its way into the lore of Arnor.

So, I have thoughts. I think the first thing we want to be thinking here is in terms of a medieval, rather than modern information environment. Tolkien's timeline is mythic in scope, but even allowing for some exaggeration there, the battle is very much out of living memory.

Yes and no; Elrond is there! Someone could just ask him! He seems friendly enough.

And it's the gaps that are odd to me. Faramir and Boromir know a great deal about Isildur and Anarion. Boromir knows that Isildur lurked about Minas Tirith for a while educating his nephew!

So, that's actually exactly the kind of patchy knowledge I'd expect! Take a look at the sources we have, for instance, for the Middle/Late Roman Republic. For some years, we have Livy *and* Polybius, and we're really well informed! But in other years, the relevant sections...

...of Livy and Polybius are lost, and all we have are later summaries of their work. Often that means literally knowing, "An important battle at <place> happened in this year and <side> won." Sometimes we're left trying to sketch out the events of a decade from...

...really disjointed biographies (esp. Plutarch) because while there *were* narrative sources for these important battles, they don't survive. And that's with a fairly complete reckoning of all of the material that made it out of the classical past.

Faramir's situation is worse: maybe the information exists, but it's in Rivendell (a long way away) and it may be in a language that few in Gondor speak. Getting that information means sending someone all the way to Rivendell - hardly a safe journey, as we see!