This is actually a pretty poor idea, considering how i havn't read the book in a while but in OoTP if i recall correctly the Headmaster's Office is sealed off to Umbridge after Dumbledore leaves. Harry wanders around at night and ends up getting into the room, guessed some kind of muggle candy probably... He then finds various things. Yea books, ancient artifiacts, mysterious letter, pensieve with the prophecy... Yeah not much to it but i figured someone could do use it.

 

McGonagall wouldn't look up there--she's not the sort of person to take dumbledore's absence seriously in that way. And, as she is the only one who has a 'right' to be there (as the stand-in headmistress), most likely no one else would have done it. Also, dumbledore's pensive would most likely still be there. he probably wouldnt have thought that there would be any reason to take it with him in the few second-long window he had to make his escape.

 

Umbridge was banned from that office; Doesn't mean others were as well. Dumbledore could pop in wherever he wanted, using either floo or Fawkes.

 

Yeah, phoenix travel needs some serious limiting in any well-balanced fic.

 

House-elf traveling too.

I wonder in which occurence Harry would be more angry? Discovering the prophecy stashed away in Dumbledore's office on his own or discovering about it at the end-of-fifth-year revelation?

Anyhow, I think that as long Harry doesn't get too angsty about finding out the secrets kept in DD's office and proceeds to make use of said secret materials in an intelligent and sneaky fashion, the story could be pretty interesting as well as readable.

 

I'm fairly certain that everyone would avoid dumbledore's office--either to try and forget that he's on the run, or out of a sense of duty. after all, he's not there to invite them in when they knock. it's part of a reutine.

 

I've seen this used only once in an AU fic:

Someone told Harry, "Hey, that prophecy was made for Dumbledore, not you! You're free, kid. He's just using you to do his dirty work."

It only works in Indy or Dark fics, but it's still an interesting and underused catalyst.

 

This doesn't need to be indy or dark fics only. Dumbledore simply sets Harry up to get into the office after removing anything he feels Harry doesn't need to see.

You could move all of the pertinent happenings in book 6 into book 5 at this point, namely the weekly meeting of Dumbledore and Harry and the revealing of Voldemort's past and of the horcruxes. Show Harry only the first part of the prophecy that Voldemort knows and tell him that he will learn the rest when he has mastered occulmency. Then tell him that he is free to come back to the office and use anything in there at any time.

Based on his past actions, Harry would probably start to prepare himself and would learn occulmency before the year has ended. Dumbledore would be seen as mentor!Dumbledore rather than abandonme!Dumbledore even if he is written as manipulative!Dumbledore. Perhaps especially if he is written as manipulative!Dumbledore.