Maybe it is just me and my group, but in a situation like this, as I described each item found a player would be writing them down. The relevant section of this writing would read like this:
Adamantine Armor, 1 suit
Gauntlets, 1 pair
Ring
Each having a brief description so that it is clear which item of that type is in question later, such as "Ring, engraved gold band set with 3 red stones" and "Ring, stylized shield device" to keep the two straight.
Then, when selling the armor the player would likely interpret "..the whole set?" as meaning all the pieces of the armor, not just some of them (like selling off everything but the breastplate). After the sale, the list of items would still read:
Gauntlets, 1 pair
Ring (and description)
So the player, knowing they didn't mean to sell those items would firmly believe them still in the possession of the party - and be rightfully agitated if I as DM were trying to insist their character had made a mistake and sold them with the armor because I decided my interpretation of "I sell the armor to the blacksmith" was "I sell the armor, guantlets, and ring to the blacksmith."
And if I did end up misinterpreting something the players had their characters do so that what I think happened and what they think happened differ? I'd say "Oh, sorry I misunderstood. Let's adjust that then, and move on." because I have no malicious or disciplinary intent towards my players.