Lung-shot deer can easily go 100 yds. Never give up on looking for a deer before scouring every bit of cover within 200 yds of the last sign. Then do a grid search or some other methodical approach. Then just look in the general direction the deer went, looking along trails, in blowdowns, ditches, thickets, sources of water, etc.

It is easy to get that "low" feeling and quit looking, but don't do it. I have found a few deer for others that just seemed disinterested in putting forth the effort to track.