I agree the only way to know is investigate it thoroughly.
As for trusting your eyes...I will have to disagree to some extent as I just experience a situation where my eyes lied to me.
Or at least my vision was somewhat deceptive. When shooting at live animals things happens so quick that without a video to show it frame by frame its hard to really know what took place in some situations.
Here's my story from Halloween afternoon. At 6:10 pm I took a shot at a quartering away doe shooting on her right side. At the shot my arrow appeared to hit her way back and in the ham about middle ways up. And with very little penetration.
She took off shot out of a cannon, and I watched my arrow fall to the ground about 15 feet away from where she stood. Upon investigating the area I found found white belly hair and stomach materials.
I backed out for 3 hours and upon returning prepared for a long night of tracking I set out to look for a gut shot deer that I originally would have said was hit in the ham.
After 50 yards of nothing but Gut materials and no blood I find a pile of intestines, large and small and the colon all piled together
From there I begin to fine small droplets of blood for the next 61 yards and a dead deer that stiff as a board from being dead for 3 hours.
The moral of this story is expect the unexpected, your eyes will lie to you and only a through search will tell the full story.
In my case the Simmons Tigershark had unzipped the lower paunch of the doe and totally disemboweled her by the first 50 yards. That's not what I saw!