Doesn't look like a bullet hole unless it was a slug from a twelve gauge. The circular indent on the out side of the shed looks about the same size as the indent in the pine bale. About the size of a broom handle. It almost looks as if someone slowly pushed the unknown item into the plastic on the outside until it finally popped through ripping the plastic on the inside and puncturing the bale of pine. Then after pulling it out they ripped it more on the out side and pushed in some of the insulation to try to see what was inside. That would explain why there is no insulation on the floor. It is not missing it is just pushed around a bit.