Car started on its own. The neighbour came to tell us. We were in the house. 
I was blaming my husband for perhaps sitting on a key or something. He wasn’t.
Then a few hours later all the windows came down. In the pouring rain. Lovely. Kid spotted it when closing her curtains.
This is off topic on an already long post. But I dont think it is a fault at all, and need not add to reliability concerns.
If the car was in silent EV mode when parked you may have forgotten to press the power button to switch the' ignition' off when you left it. It will warn you by bleeping, and not locking the car but you might not have noticed. In addition the car might still be receiving proximity signals from the key, even from inside your house. Thus the car effectively still had its 'ignition' on, and able to start automatically to keep its battery charged in the normal way.
Something similar happens when you do switch the power button off, but forget to put the car in P . Been there done that for both
I think its normal when washing the car for it to repeatedly lock and unlock itself, if the keys are outside the car but still in proximity range. So maybe if the car is left in abnormal circumstances rain can affect the window sensors in the same way.
