Mine went out in the middle of a road trip, and I drove it a couple hundred miles with a broken wire as you described -- same cylinder too, as I recall. Along with a wad of electrical tape.
I also drove it about 30 miles with the spark arcing onto the engine block from the wire until I could get to some electrical tape.
I don't see it as a big deal especially if it's not misfiring.
BTW, I had to buy the whole wire set, $150 or so (Bosch). But probably worth it since the others are likely on their last legs.