Very strange, this happend exactly with my IS220D!!!
When i was searching info about this i have read this topic, yesterday i had cleaned the EGR valve and disabling it.
I had removed the EGR, took about 15 minutos to cleaning it, after that the EGR was installed and i was trying to starat the car and... nothing append. Battery DEAD! !?!
I got a "quick battery starter", after plugged in,i was able to start the Car, run about 40 km with the car but this morning the battery was uncharged again.
I will call the Lexus dealer, because i had bought this car 4 weeks ago (second hand) and this kind of problem should be coverd by warranty.
If i hadnt read this post before cleaning the EGR i would say that was "normal", but this append like "nearlyfunny" user described