Clear your conscience and put more time looking for that deer. 6 hours is decent, but putting in a little more time will ease your mind you tried hard. You never know. If you do happen to see ravens/crows/eagles/buzzards grouping or hovering in an area, most likely your buck is there.

Also, be on the look out for similar bucks, because you just may see the same buck again and will notice the wound.

Sometimes things just don't go right.

Good luck,

iSnipe