Harry Potter
Okay, to defend myself from the black pit of Harry Potter magical mistakes, I am going to now justify my interpretation of the Fidelius Charm used by Dumbldore to hide the location of Order Headquarters.
According to the Harry Potter Lexicon, which has been acknowleged as excellent by JKR herself, and can be found here: http://www.hp-lexicon.org/magic/spells/spells_f.html#Fidelius
Fidelius Charm (fih-DAY-lee-us)
"fidelis" L. trusty, faithful
"An immensely complex spell involving the magical concealment of a secret inside a single, living soul. The information is hidden inside the chosen person, or Secret-Keeper, and is henceforth impossible to find -- unless, of course, the Secret-Keeper chooses to divulge it" (PA10).
-
Used to try to protect Lily and James Potter from Voldemort. "As long as the Secret-Keeper refused to speak, You-Know-Who could search the village where Lily and James were staying for years and never find them, not even if he had his nose pressed against their sitting room window!" (PA10) Unfortunately, Peter Pettigrew was chosen as Secret-Keeper, and he betrayed James and Lily.
-
Dumbledore used the Fidelius Charm to hide Number 12 Grimmauld Place, the headquarters of the Order of the Phoenix. He himself was the Secret Keeper for the Order (OP6).
-
Snape could refer (at least indirectly) to the fact that a Fidelius Charm applied to the headquarters of the Order of the Phoenix, but since he was not the Secret Keeper he could not mention the name of the place (HBP2).
Okay, got all that? Good. Now, I believe that the use of the word 'Find' implies just that. It cannot be found. But, if a person already knew the location of the building, then they would not have found it at all, they would have returned to it. The charm is never said to eliminate knowledge, merely to prevent others from learning of it.
Naturally, this theory may be wrong, and if it is proven wrong by JKR(has to be her, no one else), then I will change what I have written, and modify my theories, but until then...it stays. Of course, if anyone can quote JKR and prove me wrong, I will bow to your superior knowledge.
Thank you.