I'm I missing something here when cleaning the car?
I think you probably are, but it isn't purely about cleaning the car.
Your HEV has 2 batteries under the rear seats. One is a largish capacity traction battery which will propel the car periodically. The other is a small capacity Lithium battery which starts the car and runs all things electrical. When the car is switched on and the 12v battery gets low on charge, the traction battery sends a charge to top it up and when the traction battery gets low, the engine will charge it.
When you park your car and switch off the ignition, there continues to be items drawing power from the 12v battery e.g. the alarm system. Therefore, the longer the car stands unused the more chance the battery will deplete enough to cut off power to items it deems unimportant e.g. air con settings etc. If the power then drains further, you won't then be able to enter your car via the fob and you'll have to gain entry manually, press the battery reset button and then press the engine start button within 15 secs and the engine should start, after which the traction battery will send power to the 12v battery and all will be well until the next time it happens.
Worst case scenario, the 12v battery depletes so much, the battery reset button doesn't do its job and you have to call out the AA to jump start it - or do it yourself.
Now we get to the car cleaning bit. We'll assume you've parked the car for the weekend with no intention of switching on the ignition, but you intend to give the car a groom, which usually involves unlocking and opening doors and the motor driven rear hatch. All of these actions will draw power from the small capacity 12v battery and possibly deplete it enough to cause the problems I've already outlined.
You can prevent battery depletion by first opening the car and switching on the ignition. With the ignition on, the internal system will recognise when the 12v battery is getting low and top it up with a charge fron the traction battery. If the traction battery then becomes low on charge, the engine will start up on it's own and charge up the traction battery, thereby completing a continuous cycle. Therefore, when you've finished cleaning the car, you will turn off the ignition, lock the doors and the 12v battery should have virtually a full charge in it, so when you get in on Monday morning the car will start and none of the parameters you had set in the dash will have changed i.e will have reset to default.
Of course, you obviously don't want to leave the car unattended with the ignition switched on. Also, you don't need to keep your fob in a Faraday bag, as after a few minutes of inertia it will stop emitting signals that can picked up by thieves with a remote signal reader.
Forgive me if all of this is teaching you to suck eggs.