However, I have just realized that JKR left me one glimmer of hope... not about Snape, but about Uncle Alastor. You see, unless I'm misremembering, Mad-Eye's body was never found. All we ever saw was his fake eye, and that could easily have popped out when he tumbled into a haystack somewhere. Yeah, yeah, I know it's unlikely considering that Voldemort himself cursed him in the face, but work with me here.
So here is the idea I don't have time to write, but it makes me feel a little better just thinking about it: After being struck by the curse, which was not a Killing Curse because... uh... Voldemort decided to use a different and less fatal curse just for kicks, Mad-Eye fell from the sky and lay terribly injured and near death until a nice witch named Imogen Crump found him, hid him and nursed him back to health. Which took a long, long time, and happened far away from the main action so nobody knew about it. Yeah. And...
Oh drat, you can't fix injuries caused by Dark curses, right?
*shakes fist in the direction of the UK* CURSE YOU, JO!
No, not really. But it was harsh of her to kill off both Snape AND Mad-Eye, I think.