Sirius can't be dead

[sploogal]

No: HPFGUIDX 85746

Hi!  Sploogal here.
I was absolutely distraught when I read the bit where Sirius
supposedly dies - I cried for hours!  (He was my favorite character.)
 I refused to even look at the book for a month afterwards.
I've been doing some thinking though, and I don't think that he really
is dead at all - it just seems that way.
First of all, the whole of PoA centres around Sirius and introducing
him as James' best friend and a very loyal and trustworthy person. 
Yes, PoA is about other stuff as well, but one of the main things in
it is Sirius.  If JKR has devoted an entire book to Sirius, it seems
unlikely that she would kill him off two books later without a really
good reason.  Can anybody think of a really good reason as to why
Sirius had to be killed?
I can think of a lot more reasons for him to stay alive, one of the
most important of these being that he's a father-figure to Harry. 
He's the person that Harry turns to for advice and comfort.
Also, in GoF, when Cedric Diggory was killed, it states that "He was
dead." immediately.  Other characters later say out loud that Cedric
is dead.
When Sirius 'dies', nobody actually says out loud that he is dead
except for Harry.  You'd expect Dumbledore to say something about it,
wouldn't you?
Lupin saw Sirius 'die' and seemed to react a little to calmly to the
loss of his last remaining friend from his time at Hogwarts.  Perhaps
that is just because of the type of person that he is, or he was in
shock, but I don't think so.
Another interesting point is that the curse that hit Sirius was not a
killing curse - it was just a stunner.  Sure, it sent him flying
through the veil, but we don't actually know anything about the veil,
do we?
Hmmmm... maybe I'm still in denial, but I really don't believe that
Sirius is dead.