This has bugged me for ages.
Dresden killed Susan. She had just killed someone and was becoming a vampire when she died.
Dresden, shortly after, died himself. Via the train he learned there were different places people ended up.
He met ghosts, he met angels.
He never asked what happened to Susan. He was bothered that he'd killed her, but he never sought any knowledge on where she'd gone after he killed her. Logically, the guilt would be eating him up, we even see that it's the case in a later book.
But he never asked if this woman, the mother of his child, one of the true loves of his life, who had just commited murder and was losing her humanity as she was killed, by him, went to whatever counts as heaven, or hell. He never got what I would have thought of as a massive piece of closure and it never even crossed his mind in the book to ask.
This is one plot point that just bugs the heck out of me and it still isn't resolved.