Having flown a ton of OZ flights over the years, this has never happened to me. They do always seem to serve business class from first row to last, so if they did run out, it would naturally be at the last row. I generally prefer sitting at or near the back myself, so think if it was very common at all I would have experienced it at least once. Maybe I'm just lucky. I've had numerous occasions where they ran out of my first choice, and I had to settle for something else, but still from the business class menu.

In economy, likewise I've never been left without a meal, and I haven't been left with needing to chose a second choice for a number of years, perhaps being I'm usually up near the front when in Y.

Now if for some reason they had a very light load in C, but ended up with lots of op-ups at the last moment, then I could understand them running out of meals, but I'd think in that case they'd single out the op-up passengers and serve the paying/award customers first. My best guess is that it was a one-off deal where something went wrong with the catering for that flight. I'm sure it's bound to happen on a rare occasion where the food doesn't get loaded, wrong food gets loaded, or the food is somehow compromised after being loaded.