Dumbledore has one. :) My theory is that the message from McGonagall to Flitwick is going to pass through many hands (or pockets), including Dumbledore, Snape, Quirrell, several versions of Harry, and at least one use of Harry's patronus.
You gotta understand, this is Eliezer doing the plotting here.
Of course, a different trick that could be used, if necessary, would be to bring a fresh time-turner (or several) back from the next day. I'm sure Harry has already experimented with what happens when you carry a time-turner back from just after midnight, and then hand that freshly recharged time-turner to an earlier version of yourself. Can a time-turner be transfered back in time? I'll bet Harry knows. Harry is already familiar with puzzles involving trucks leaving caches of gasoline cans in the desert. The Ministry of Magic is not.
Harry has likely not yet experimented with taking time-turners back in time. He stopped all time travel experiments after he got the warning about not messing with time.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.