I would counter this by simply pointing out that the responses by the players was the most telling. Anything that causes feelings similar to those apparent to the OP between the players, or the players and DM/GM, are something to be thought hard about. The game is there to be fun with your friends, not to be a cause of strife and hard-feelings towards each other.
That said, I've made similar mistakes in the past. It has universally turned out to be far more negative than positive and leads to stupid defense mechanism-type gaming habits that not only tear the players from the narrative, but makes the telling of a great story a distant second to making sure "they don't screwed again" if such bad decisions continue to happen.
You can beat the situation to death with arguing details, but at the end of the day you hurt your game if you run it this way. For those that do, stop doing it for a few months. You will find that your game is far better for it, both narratively and in the overall stress of running the game.
Yes, but the response by the players described by the original post differs from the response described the the DM in the expanded account and his later posts. The best I can tell from all of those is that the barbarian and monk were annoyed at the ranger (player) for making the mistake, and even more upset about selling another set of armor they specifically told him not to. The ranger player was upset for making the mistake, not at the DM for the situation. The sorcerer (cell phone guy) was annoyed at what? It's not clear and he apparently wasn't available for further clarification.
And in my "universal" experience, I haven't had any sort of "more negative than positive" reaction nor any "stupid defense mechanism-type gaming habits that tear the players from the narrative." The only mistakes I see here is potentially not providing enough of an immersive experience (hard to tell from a summary) and failing to engage the mechanics of the game more frequently.
So I completely disagree that "I hurt my game if I run it this way." It's all about the players at that table, and how things are handled. The only real question as to whether it was "right or wrong" was that the DM realized the player forgot and/or didn't remember something and used that to the smith's advantage. I look at it this way - the smith has no idea what the ranger does/doesn't know. Whether the description was sufficient or not is really unknown, but the mechanics are there to help address the difference between player and character knowledge. The DM stated that the way he runs the game, it's up to the PCs to know what they have.
What changes could this implement in the players?
Better communication between them.
Paying better attention.
Making better notes as to what they have.
Be more involved in NPC interactions.
Yes, these are horrible things to expect of the players, and certainly would tear any game apart, and would obviously sacrifice any chance of maintaining a great story.
Sure, they might be more suspicious of NPCs, but that's generally pretty normal. The only real problem I can see is if the players think the DM is taking advantage and punitive towards them, and other than the sorcerer where it's not clear, I just don't see that as the case here.
I should also note that I get the sense that people are taking this particular situation
way too seriously. That's extremely common when discussing something online and outside of the actual game and circumstance that sparked the debate. A single event like this, among best friends as described, in the course of many, many hours of play, and probably more hours outside of play doing other stuff, is generally not that big of a deal. I can definitely see in a public game, with people who don't know a particular DM how this could be very different. This could be a bigger deal for a public game.
But if you're playing with a bunch of friends and losing the possibility of owning one or two magic items is that big of a deal within your game, there's probably a lot more going on than this one situation.
I agree that we've beat this to death. Don't recall the last time I had any stress running a game, nor the last time there was any significant discord within the group regarding my DMing and such. We're there to have fun, and if something doesn't feel right we deal with it. To put it differently, I've never been involved in any situation running a game where I would ask the greater community "was I wrong?" And it seems I'm not always on the popular side of discussions here at Enworld (like this, DM fudging, whether dragonborn are common or should be in the Forgotten Realms, etc. ). None of my "unpopular perspectives" here which are fully incorporated in my campaigns have caused any distress that I'm aware of. With my home or public campaigns. As always, YMMV, they aren't for everybody or every table. But they work for us, and my home campaigns tend to run for years (we're on 1.5 years for this one, the last was 8+).
Ilbranteloth