When Hopper and Jane went back to the laboratory, they found the doctor who had managed the project. He was in a stairwell, having previously been left in the security camera room.
Most curiously, he appeared to have been stabbed by a Demogorgon claw, and even gnawed on a bit, but he was still quite alive—all this despite having been in the building for hours, having been grievously wounded to the point of immobility, and having no weapon. Crucially, of course, he’d already had an encounter with at least one Demogorgon, and had been left at their mercy. And we know that the Demogorgons don’t tend to leave their victims for dead, either—quite the contrary, they appear to be more “strip the bones of flesh” type monsters. It’s not as if they weren’t in the lab, either: by the time Hopper got downstairs, there were dozens of them.
Why didn’t they kill and eat the doctor? Was he just lucky enough to evade their attention after getting nearly killed, and if so, how? Or is there something else going on here?