My question: aside from visually tracing each wire, does anyone have a procedure that they use to ensure that each box has been feed?
YES! Ring it all out... Take one large (annoy the whole neighborhood sized) doorbell and transformer. Remove all the beakers and feeds in the panel. (Especially the neutrals) Then take all the branch circuit hots and wire them to one side of the transformer, the other to the bell. And take the other side of the bell loop and connect that to all you neutrals. (If you isolate the buss, its easier if they are all connected already...) Then go to each outlet (and close the loop like a switch) by shorting hot and neutral... Close the switches and check each lighting outlet too. when you short the wires, you hear the bell ring, and you know you have a hot and neutral. If you can isolate the grounding for the panel and not in metal studs, you can do the same for grounds too. FYI you CAN NOT do this with low voltage lighting! for that you need to power them, and put a lamp in each one...
But either way, I would video the install, and make a full line diagram
of the whole place before rock!