I've noticed this a few times. Today, my battery is dead as I guessed it would be. The dead battery seems to happen when I spend more than 2 days without driving it. I last drove it Friday evening. About to call AAA for a jump, then drive it around a while.
It has the lights that have a sensor on the dash that senses when it's dark, but they're only supposed to come on when the engine is running.
I don't know how often this is happening. Occasionally when I've noticed it I've tried using the fob to arm and disarm the alarm. This will shut the lights for a few, then they come back on.
I'm starting to think I should maybe shine an LED light on the sensor at night when parked.