If you hit him in one lung, keep looking. Don't give up.
On October 8, 2009 I shot at a buck at 7 yards. After the shot it jumped up in the air and kicked. It took off running to the northwest. I thought I made a heart shot but when I retrieved my arrow I saw red blood mixed with guts. WTF I exited the stand and left to the southeast. Long story short... the buck, button-hooked back and I bumped him from his bed when I exited the stand. I found him the next day 0.77 miles as the crow flys to the south of where I shot him. I used a GPS to get the distance from where I found him back to the stand.
I figured he traveled close to a mile before he died.
A few years ago I shot an eight point that I thought was a good hit. It was high, but i thought it was in the pump house. We even had fresh tracking snow. That buck just kept going and going and the blood stopped. About a month later my friends sees the same 8 point feeding in his food plot with a healed patch high and another healed patch down about halfway on the right side. My arrow must have traveled over the spine and exited along the ribs.