This is why I asked, upthread, whether the blacksmith had a ring of X-ray vision. If not, how did he see the gauntlets and ring yet the ranger not see them?
Because the best I can tell from the description, the barbarian handed the ranger a bundle of armor, which he simply took with him. He didn't examine it, or anything of that nature. He saw the bundle of armor, of course, but that doesn't mean he noticed the ring or that the gauntlets were different. Once the armor was tied up, whether the gauntlets were visible or not is unknown. The blacksmith, on the other hand, did examine it. I can think of all sorts of possibilities for him to prevent the ranger from seeing it at that point. If I was DM, I would have given the ranger a passive Perception check against the blacksmith's Stealth, or perhaps Deception, unless the ranger was specifically suspicious of the blacksmith. Then he might have rolled a check.
One of my daughter's favorite shows is Brain Games and you'd be surprised at how many things in plain sight that we don't see.
But unless the ranger or the party (who spoke up about other things) mentioned that they were doing something different with the gauntlets, the possibility exists. Part of the problem I have here (not necessarily you) is that some people seem to think that any clue that wasn't enough to guess, or an outright "what about the gauntlets" is insufficient. I disagree with that. They made a mistake, the blacksmith attempted to capitalize on it, and they had an opportunity to figure it out.
My only potential criticism is that I would have had a much more involved interaction, with additional checks. At its heart, though, it's a simple Deception or Stealth vs Perception check.
Ilbranteloth