Where is this battery draining code from?

During waking hours the other day I noticed the messagesgui was open and didn't time out to the clock face. The screen was locked and lcd backlight off - could be unlocked and backlight turned on with hw button press. My experience was that this state had a high draw of the batter for some reason - even though it feels unwarranted (the watch was just sitting on one of the messages - shouldn't be very battery intensive..).