Welcome to our world Marianne. Gripper and I have both discussed this problem elsewhere. I would send an email to
nnaconsumeraffairs@nissan-usa.com to reinforce this problem. They have big liability problem due to the carbon monoxide generation in a closed garage. If you don't have an CO monitor (like a smoke detector) then I would get one today.
It happend to us when my wife parked at the airport and was late. She left it on and the headlights in Auto. So the ICE would turn on periodically throughout the day and at night the lights would come on. Once the gas gauge hit E, the ICE stopped coming on and when we returned both the 12v and HV batteries were dead. I documented that experience elsewhere here. (this also killed our mileage performance for that tank of gas!)
You really have to form a habit of making sure the car is off when you walk away.