In the Unfinished Tales there is the brief story of The Disaster of the Gladden Fields in which the events are told of how <PERSON> and his sons together with some of the top soldiers of Arnor were wiped out, as well as how the tale made it to Arnor and Rivendell (but apparently not Gondor, unless much later in shortened or garbled form, maybe)
It's mostly written from the POV of the "omniscient author" as it describes events which nobody survived except
a young esquire stunned and buried under fallen men.
He is elsewhere named as <PERSON> and he
heard the words of <PERSON> and [<PERSON>'s eldest son and heir] <PERSON> at their parting.
<PERSON> was in <PERSON>'s full confidence as stated in a footnote. Those words in an earlier paragraph are described as
[...] And we bear burdens of worth beyond all reckoning
and later <PERSON> asks his father whether he couldn't cosplay as <PERSON>:
what of the power that would cow these foul creatures and command them to obey you?
To which <PERSON> replies that he found out the hard way that he can't use the Ring and can barely even bear the pain of putting it on. He doesn't have the power to use it and it therefore should go to the Keepers [of the Three Elven Rings]
Later still, <PERSON> tells dad
Go! Take your burden, and at all costs bring it to the Keepers: even at the cost of abandoning your men and me!
By then, two others of the three overall survivors had already left, with one being <PERSON>. One paragraphs says
<PERSON> turned to his esquire: "<PERSON>" [...]
Esquires, according to Wikipedia, before their definition of being more like "gentlemen" (e.g. 381
of the landed gentry) were
personal attendants of Knights of Orders of Knighthood, this title is held by all attendants on the person of the Sovereign,
or
A young nobleman who, in training for knighthood, acted as an attendant to a knight.
Wikipedia: Esquire
<PERSON> would therefore have been quite close to <PERSON> in daily interaction. Helping to get dressed, shining boots and armour, that sort of thing. A *gentleman's gentleman" as <PERSON> would put it. It's hardly beyond doubt that he therefore would have seen the
small case of gold, attached to a fine chain
which
beyond all doubt [...] had once borne the Ring around <PERSON>'s neck.
Whether <PERSON> saw the Ring itself (and somehow resisted the lure due to willpower and out of sense of duty) is possible but speculative and not mentioned in the brief text.
But between <PERSON>'s and <PERSON>'s tale (and of course the Wise knowing full well that <PERSON> has held on to the Ring and it was now gone), those in the know would have pieced together that the malice and draw of the Ring would have brought the Orcs and led to <PERSON>'s downfall. It being his Bane and the outcome of his hubris. 381