Deer hit too far back walk away slowly with their tail clamped down (sometimes twitching from side to side) but with a gun at forty yards, even a gut shot doe would bolt from the sound of the gun shot. I' m betting on a gut shot or a liver shot that just barely touched the liver. Her reaction makes me think that. Was she hunched up? Did she walk funny? It is tough to tell without seeing anything but I agree that the clump fo tissue is either a blood clot or a piece of the lobe of the liver. Liver hits are funny. I have centered the liver and had the deer die in fifty yards just like a lung hit deer. I have also shot completely through the liver and had to finish the doe off the following morning. (both bow shots) In any case, don' t give up, that blood trail didnn' t come out the other side of the thicket! A gun makes a bigger mess of whatever it travels through than an arrow does. I like your chances.

Greg