You would not signal net fault for something on the opponent's side of the net. You would signal reaching over, which is another reason you can't cite this rule in the original situation.

But hey, in your match, you do whatever you want.

The correct signal in this case would be "reaching over".

That signal, as stated in the officials manual (2016-2017) is to be used when

* A player illegally contacts a ball which is completely on the opponents side of the net
* Contacts an opponent over the top of the net.


So yes, even though the contact occurred below the net, the ball was still illegally contacted on the opponents side of the net. The correct signal is "over the net". I would then expect have an explanation as to what was witnessed for the captain who is very likely to question the call.