In my experance I' ve always gotten a hollow thud sound on a good hit. It' s kinda hard to describe if you' ve never heard it. A hollow thud is about as close as I can come. Once you' ve head that sound you' ll never forget it.
Did you search in the morning with better light? If you hit sounded solid I would belive you had hit bone if it was the deer you hit. I always try to get a good line on the shot and search closer and beyond where you think the deer was standing. Ofter times I' ve found the deer to be as much as ten feet further away that I thouth it was when I shot. This may help to explain the lack of blood. If your searching for blood 10 feet from where the deer stood you could look for a long time without much results.
Where you hunting from a tree or the ground? When I hunt from the ground I find that I misjudge distances more often than I do from a tree.
I' d try to get the best line on the shot possible and comb that line for sighns of hair, blood or your arrow....chuck