[Adam]

Three possibilities that I can think of.

1. A6 was injured.
2. There was a significant delay before the first shot (maybe (a) a timeout, (b) a blood spot, (c) A1 was starting to lose his composure and the officials allowed the sub to happen right away, or (d) a walk to the other end) and the officials brought in the sub early.

Not that I recommend (d), but I've seen it done, and I've done it without thinking a couple of times.

3. The officials screwed up and waved him in without thinking.

Also, just to be clear, the officials were correct not to allow him back in.