Don't give up just yet. What are the circumstances of the lost deer? No blood trail? Blood trail stopping and starting? How did you search for the blood trail? The best way is to find approximately where you shot the deer, and start walking in ever expanding circles. If it's a scant blood trail, start walking those circles where you last found blood. Make sure you carry a black light flashlight for low light situations, it makes life a lot easier when it comes to spotting blood. It's a tedious process, but it makes the hunt even more rewarding. I'll admit, I've lost deer, but it was usually my fault due to inexperience, although sometimes It doesn't matter if you have 100 years of experience, you'll go home empty handed.