where did the coolant go?
 

first, back story.
a month ago i blew a heater hose and over heated the engine.
i replaced water pump thermostst, and while i was at it i replaced the knock sensors.
i bled the coolant system the correct way ( with the yellow funnel)
now here it is a month later and i have a low coolant message, im a little less than a half gallon low. i have check every where for leaks, water pump steam pipe, hoses, no signs of a leak under the truck?
now i notice when i first start the truck it blows white smoke out the exhaust until it warms up?

Im gonna venture to say you probably warped one of the heads when you overheated. Not much, but enough to cause coolant to leak into the cylinder until the block and heads expand enough to seal again.

yep...leaking into the cylinder, have the heads milled flat and new headgaskets