What is it with this thing in the 4th harry Potter book ?

okay you remember when after harry went to the grave yard... returned... and Dumbledore was questioning about what took place there ? now... do you remember when J.k .Rowling wrote that for a fleeting second harry saw a look of triumph in Dumbledore's eyes ? well, I was wondering about that. and I know all about Dumbledore and harry being religious figures... I've read the book "finding god in Harry Potter" but if you could answer nicely I'd appreciate it... thanks =]