The Sorting Hat could provide the sword from wherever it was. It's magic, you know. When Harry pulled it out to fight the basilisk, nobody had put it in there beforehand.

Admittedly, JKR kind of glossed over a lot of things in this last book, either to get it done on time or to build up a market for the Harry Potter encyclopedia-to-come in which all will be made clear.

For instance, the Ravenclaw tiara artifact that was a horcrux was almost ridiculously easy to acquire and destroy after the first ones needed over a book to get to.

Been rereading the books in reverse order lately and I have a question: Why couldn't Harry see the thestrals pulling the Hogwarts carriages at the end of the year in Goblet of Fire? He'd seen Death by then (when Cedric Diggory got snuffed) and the next book made a big thing about Harry seeing them when he returned that Sept ember and thinking he was losing his mind. For that matter, hadn't he seen Death when his parents were killed in front of him? Or with Prof. Quirrell in the first book?