Lotsa confusion here. Firstly, the solution of just measuring an adjacent spoke and getting a new one is sound. It is basic stuff and spokes on crappy wheels are mere consumables.
Now for torsion, torque, opposite sides, crazy lacing etc.
1) Radial spokes cannot transmit torque.
2) A wheel manufacturer can make torque go through either the left or right side of a wheel.
3) Hubs with slender mid sections cannot transmit torque to the opposite side of the chain because small diameter tubes are poor at transmitting torque.
Therefore, the picture of the Mavic hub above tells us a few things. a) the torque is transmitted through the left spoke flange. See rule 1 above. The manufacturer knew what it was doing because it made the torque tube (hub centre) large and thick. I use right and left here as in the bike's right and left, not the picture above that's flipped.
Why do they do this? Because you guys (if the shoe fits and all that) insist on weighing your components and the mantra is "lighter is better".
By putting fewer spokes in a wheel you can make it lighter. Unfortunately fewer spokes compromise durability because spoke life is a function of cycles (miles) spoke tension (which is a function of quantity) and load. On a rear wheel there are two types of load to contend with namely your lard ass and your pedaling torque. Both these factors fatigue the spokes and they eventually break. Front wheels only contend with weight.
What Mavic has done in the example above, is to put the torque only through the lower-stressed (tensioned) spokes on the left by making the right spokes radial. It is an attempt to protect the right spokes from both weight and torque and let the higher-count. They could of course have done away with all this nonsense and just built wheels with enough spokes and all crossed. But that would not be glarly enough for hard-core racers. Campag, as much as I love the company, does similarly stupid things and I sometimes wonder where marketing and engineering should meet when it comes to these things.
