Check out the edge of the cloth- it is very thick.
If the doll was the size of a human, that would be some very thick cloth.
I also doubt the terrorist would let the solder continue to wear his bullet proof vest. They probably would have made him take off his knee pads, and I bet they would have put him in non-military cloths. They couldn’t take a chance that he might have a weapon hidden in his military uniform.
Most hostage pictures I have seen show the victim on their knees and the kidnappers like to be in the pictures unless they are close-ups of the victim’s face.