Happens to all of us some of the time. Had two this year early season that did the same. No blood until they dropped. Hole through both of them and good placement. Sometimes they just bleed inside and nothing where they are hit. Is worse when there is no snow. Mine were in the evening and right at dark. High weeds and no blood trail. Walked for 2 hrs and nothing until morning and too late then i the warm weather and coyote territory. Never lost 2 in the last 10 years but happened this year. Mine were found about 75 yds but not that night.