It is a conjuration spell with d&d standards Insomnia.... meaning the items are treated as the actual thing. Meaning the stew will fill and give the group just as much energy as a regular cooked one.... also the campsite being there isn't what is draining Heinrich of energy. Its the enormity of the special that drained him. The campsite will continue to be there until he dispels it. Also the moonlight is shining into the room... the only thing that would light up the place until the camp was summoned is Heinrich's staff.