For the last few days, I have been printing a variety of things. I’ve printed in Regular PLA, Matte PLA, and ASA, with no issues. The weird thing is - I had my slicer set for my 0.4mm Nozzle, yet I actually had a 0.2mm Nozzle installed. I only realized this when I was cleaning my shelves and found my 0.4mm Nozzle.
So here is the question - why did this work at all?
“Work at all” is a highly subjective description. Post a picture.
If it printed like you would have expected it to normally print, either you did have the slicer set to 0.2mm when you sliced it for printing or the nozzle on the printer is actually a 0.4mm nozzle. Can’t think of any other options…
It is possible to create a line wider than the nozzle by extruding more material and allowing it to spread out a bit.
That will be what was happening in your case - as the printer will still have been attempting to extrude enough material to fill the 0.4mm gaps.
My X1C came with a spare 0.4mm nozzle. Are you sure that’s not the one you found on the shelf? Stranger things have happened. 
I’ve done this before without realizing it. I had forgotten I had my 0.2 nozzle installed and had configured my slicer for the 0.4. Most prints came out perfectly fine and so I didn’t realize right away I had a problem. The issues started appearing when I needed to print steep overhangs or long bridges. I won’t go into the embarrassingly long time I spent troubleshooting that, but know that it took me too long to figure out what was wrong. From what I could tell, the 0.2 nozzle gets over pressured when trying to force the amount of filament needed to print with a 0.4 and so it can’t reliably print overhangs/bridges. Otherwise it worked rather well.
Over pressured not really but it will put more load onto the extruder stepper, thinner wall may get pushed away and overhangs definitely will suffer since there is a reduced overlap to the previous layer line but otherwise just like you can print 0.8mm lines with a 0.4mm Nozzle it would be no problem to also do a 100% over with the 0.2mm Nozzle.