How to identify a fixture/outlet and wiring to breaker as knob and tube?
K&amp;T could be at any point in the run, the circuit could start romex, then switch over to K&amp;T and then switch back over to romex (potentially with a ground pulled from another circuit). 

The only way to be completely sure no K&amp;T wiring is in use is to find and trace all of the circuits and visually make sure.