Flight Instructor reported while descending to simulate an off airport landing for training they flew near a vehicle parked in the vicinity.

Narrative

Instruction flight with student on lesson for simulated emergencies. On the 3rd emergency approach to landing on final descent a silver car hidden in the shade that was unseen appeared. I checked before pulling power to idle and checked for no persons property or vessels. I then additionally checked the point on a road my student picked for anything that could put us or anyone in danger as safety is constantly running through my head. During the approach I kept a vigilant eye out for anything besides natural terrain. On final approach we spotted a silver looking camper van completely hidden in the shady area of trees. It was completely invisible even after the go around. Upon seeing the car; I took controls and immediate initialed a go around. I'm don't believe so but in the aire of caution and awareness we could have gone below 500 feet AGL during the full power transition with my focus on getting the airplane climbing and not looking inside at the altimeter. For the future; extra emphasis should be put on less distractions throughout maneuvers close to the ground.