After the search action is resolved as a success the secret door exists in the fiction, which for the purposes of these discussions means it now exists as an element of the game being played and - even though it's not sitting there on your game table - is still going to have influence on what happens going forward in the game. (and if you must keep it real-world, it'll probably cause players to say different words than they otherwise would have)
To say otherwise is nothing more than obfuscation. We're all completely aware that none of the imaginary stuff exists in the real world, but what exists in the real world is utterly irrelevant when the point of the conversation is what exists in the fictional world and by whose authorship and-or what means it comes to be there.
In the Sherlock Holmes stories, Holmes from time to time meets charaters who, up until then, have not been written about. From the point of view of the reader, they are
new characters. But no one asserts that Sherlock Holmes's meeting of them
created them.
The same is true of the secret door. The PCs' discovery of it didn't create it. The engineer and stone masons who constructed it created it. It has existed, in the fiction, from the moment of that creation. Although no
audience or
author of the fiction knew that. Just like Conan Doyle didn't know about Sherlock Holmes until he wrote about him. But Holmes himself was born, had a childhood, etc.Denying
that is what is obfuscatory.
It doesn't exist in the fictional world until it's been established, either. So there's no reason to favor one authorship or timing of that establishment over another, innately.
RPGing has always involved a degree of flexibiilty in the timing of narration. Even back in the high-water mark period for dungeoncrawling, stuff got made up (eg "What colour is the roof of this room?" "It's brown-grey stone.") No one said that the roof had no colour unitl it was described by the GM!
The secret door is the same. Descbring it, and making it up, are things that happen in the real world. In the fiction, it was always there, and it's just a misdescription to say that the PCs, by looking for it, brought it into existence - anymore than the PCs, by looking up, made the ceiling be brown-grey.
Just what is it that you hope by making comments like this? It's not as if you didn't know what I meant.
I'm hoping to get you and [MENTION=29398]Lanefan[/MENTION] and [MENTION=48965]Imaro[/MENTION] to agree that discovering the door isn't the same as creating the door. And that there's nothing remarkable about a new element being introduced into a fiction although, at the time the audience first learns of the protagonist's encounter with it, it already existed within the fiction (eg an adult met by Holmes for the first time).
If DM-facing, once the secret door is established it can begin to pressure the other fictional elements even if the players are unaware of its existence. If player-facing, it won't.
This is true.
One technique in "no myth"-type GMing is to keep introduced elements somewhat flexibile - or, at least, no more fully narrated than the situation needs. This then allows scope for integrating newly-established elements into already established elements of the fiction. Eg if, when the secret door is discovered by the PCs, a mysterious NPC had already been in the scene, and the method whereby that NPC entered the place hadn't yet been established - well, maybe s/he came through the secret door!
Keeping track of these elements of the fiction, and interweaving them to provide continuity while keeping the focus on "the action", is part of the job of a "no myth" GM.