Boing said:As for the CoS letter Harry gets in the Burrow, I think that Dumbledore might have heard from Mrs. Figg that Harry left. She might have been awake or woke up because of the car flying through the air and let him know. Just an idea.
That's a possibility. It could be too that Dumbledore went to check on Harry, as I believe that he did many times over the years while Harry was at the Dursley's. Harry was locked in his room after the pudding incident for three days - he was at the Burrow for a week when the Hogwarts letters came. It could be during those 10 or so days that Dumbledore chose to check up on Harry, invisibly of course, and found him gone. (This is just my idea -- I'd like to think that Dumbledore cares enough for Harry to pop into the Dursley's from time to time just to see how he's getting along. )
I wonder if that scene doesn't go back to how the owls know where people are even if they leave one place and go to another. In the movie it was shown that Harry's letter came in the envelope with all the Weasley childrens, but in the book he got his own envelope. In the book Mr. Weasley mentioned that Dumbledore already knew that Harry was in the Burrow, but wouldn't the owl deliver his letter wherever Harry was at the time?