I know you said there was not a lot of cover, but I think 30 feet (if that's really the actual height) is generally too high. It can lead to more "one-lungers" than you want. A deer hit high will often not leave much sign, even after quite distance. Don't let lack of blood on the ground make you think he's not dead. You say the woods are big, but ask yourself where an injured deer would go. Thicker than average areas, blowdowns, sources of water, ravines, etc. Also, do not overlook a small patch of cover in an otherwise open area. I have found deer in very small clumps of brush/weeds out in open fields. Deer like these because they can see something approaching from any direction. Keep at it.