I'm definitely a bit confused on how this is expected to work, unless the additional money is for bribing Professor Flitwick (which seems unlikely to work), seeing as how McGonagall explicitly asks whether Harry gave him the message. Then again, if he doesn't know what is being tested for, he might not know that its not being delivered in person is a problem... though he would probably find Margaret's insistence that she was delivering a message from McGonagall on behalf of Harry a bit strange - normally you just specify who the message is from and who it's to; why would he care about an additional messenger? OTOH you would expect this sort of testing to be not so unusual and thus expect Flitwick to know what was the point was.
...yeah, I'm definitely still confused about this. Alternative hypothesis: Harry has failed McGonagall's test, he just hasn't heard about it yet.
EDIT: ...oh. I just realized she would be conveying the message to Harry, not Flitwick. Nevermind. I ignored that possibility. (Assuming he was there at 3 PM...)
Harry picked up the message in the empty class room while invisible, decoded it and told Flitwick the message. He was already waiting there because Quirrel had anticipated that he would be subjected to a test of this sort. It's all in the chapter.
Update: Discussion has moved on to a new thread.
After 61 chapters of Harry Potter and the Methods of Rationality and 5 discussion threads with over 500 comments each, HPMOR discussion has graduated from the main page and moved into the Less Wrong discussion section (which seems like a more appropriate location). You can post all of your insights, speculation, and, well, discussion about Eliezer Yudkowsky's Harry Potter fanfic here.
Previous threads are available under the harry_potter tag on the main page (or: one, two, three, four, five); this and future threads will be found under the discussion section tag (since there is a separate tag system for the discussion section). See also the author page for (almost) all things HPMOR, and AdeleneDawner's Author's Notes archive for one thing that the author page is missing.
As a reminder, it's useful to indicate at the start of your comment which chapter you are commenting on. Time passes but your comment stays the same.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: