The Blocked Passage Revisited

In part one (the revamped version) of my predictions posts I talked about (many things) Snape and his possible relation to Irma Pince. Well, I stand by the basic idea, however I got a fact wrong, and I want to clear it up. Here's the excerpt from the previous post:

A secret passageway on the fourth floor of Hogwarts was blocked off sometime after Severus and the Mauraders left Hogwarts but before Harry started attending the school. This blocked passageway will turn out to be connected to Severus Snape. As an extention to the above part (Snape's relatives in hiding idea) I believe the blocked passage's location, relative to the library, means it's a particularly good place for Dumbledore and Snape to hide Snape's relatives. It would also be a good place for Snape to hide. This also leads to my next prediction....

I had said the passage was blocked before Harry attended Hogwarts. This is not true. When Gred and Forge (heehee) give Harry the map they tell him about 7 passages. Four of them Filch knows about, but the twins don't explain to us where these passages are or where they lead. Another passage is under the Whomping Willow and goes somewhere into Hogsmeade (turns out to go to the Shrieking Shack). Another passage starts at a statue and leads into the stockroom of Honeydukes. The last passage is on the fourth floor. The twins don't say where it leads, but they seem to think this unnecesary info, since they haven't been able to go through it since "last winter". Last winter would be during Harry's second year at Hogwarts. This would be around the time Harry and Ron impersonate Crabbe and Goyle to interrogate Draco.

By this time there had already been basilisk attacks. Though the first time the chamber had been opened had already taken on the characteristics of a tall tale, even a myth, Dumbledore knows it happened (he was teaching Transfiguration at Hogwarts at the time). Many of the teachers are too young to have been there at the time (as either professor or student), but I think Snape knew something about it. Lucius sure knew, since he planted the diary on Ginny for this exact purpose. Lucius and Severus having such a long, apparently chummy, history together, perhaps Lucius had told Severus about it -- not about planting the diary, not even about the diary's existance -- but how Voldemort boasted about having opened the chamber while he attended Hogwarts... and how he was the last of the Slytherin line, he -- and only he -- could open it again some day. If this is the case then Snape might have suspected Voldemort's direct involvement this time around, too, making Snape think Voldemort had already returned in some form (even though the mark on his arm would still be quite faint). If he's truely hiding his family from Voldemort and the Death Eaters he might have chosen winter holiday as an opportune time to block the passageway. And why? Well, if this passage was chosen as a hiding place for himself and any family members he might have at Hogwarts, then he might have been making some final preparations to this chosen hiding place.

There's only one thing that's really bugging me. Ok, it's a person, really. Percy Weasley. When Harry and Ron (Polyjuiced) head towards Slytherin's common room they run into Percy. Ron and Harry assume Percy is trying to catch Slytherin's heir himself. The readers start to suspect Percy has just come back from a rendez-vous with his girlfriend. However, she's not in Slytherin house, so why is he snooping around down there? I know that this scene takes place down in the dungeons, but we don't know where that passage leads from the fourth floor. I can't completely rule out the idea that Percy came through that very passage and blocked it himself.... And though I don't know why he would do such a thing, we can all agree Percy's been acting more and more strangely, and it's not just teenage hormones kicking in. The potions book plotline was removed from Chamber of Secrets, but we still have two possible book-related plots going on here: Tom Riddle's diary... and the prefect book Percy was reading at Flourish and Blotts. Ok, so maybe Voldemort isn't hiding behind some F&B's bookcase, but something horrible might be on the shelves....

I must think some more... and re-read some more.

Correction 1: Though Penelope is in Ravenclaw Harry and Ron ran into her near Slytherin house's common room before they ran into Percy.

Correction 2: Percy found the prefect book at a second-hand store, not Flourish & Blotts.

Addition 1: Another possibility (like we needed any more) is that Ginny blocked the fourth floor passageway while being possessed by the Voldemort from the diary (Diarymort or Voldymem).

Addition 2: Is the blocked fourth floor related to the rubble Harry, Ron and Lockhart find in the tunnel leading to the chamber?