not sure if this is properly intuitive, but if there were droppings ALL over, could the chicken have been chased by something or scared by something ?
another think -- you have kids, did you check their toy boxes ?
is there anything in your house that might have had a lid that closed if bumped ... bread box ?
this is way out, but be sure you check the dryer vent !! have had two mice and one rat in ours ... oh yes, check IN the dryer and the washing machine !
could be that the chicken is trapped or caught where it cannot be heard