Open Neutral Circuit yet all circuits outlets and wiring appear connected
I have two questions.. Is there a box with neutrals wire nutted together? Second, Is there a fixture on the circuit? Ceiling fan..light...
I have actually seen certain smoke detectors cause a loss of power.
It seems like you covered most areas as I would have.. The only other things I could recommend would be ohm out the outlet after removing it from circuit. Test actual wires for power after removing outlet. If no power to wires then its usually left or right of bad outlet. Also if there's critters around they could have bit threw a wire. Furry tail tree rats love eating wires in the attic