GM Can't See Whispers

Two of my players frequently converse in Infernal so that they can make plans without the other players overhearing, talk trash, and overall just make great RP using the Whisper function. My problem is that I should be able to see these whispers as I am listed in the "controlled by" field of both characters but when they whisper each other, only they get it and I as the GM cannot see them.  It may be a setting issue within the game but almost everything is on default settings and I haven't been able to track down what setting may be at fault after no small amount of looking. I have asked the players and they're directing their whispers to the character names and not the player names so I should, as far as I understand it, be able to see these whispers. Having to switch to another platform for these messages is rather clunky and has been hindering their RP somewhat.  TL;DR: Two of my players are whispering each other to simulate having conversations in a language that no one else in the party knows but I, as the GM cannot see these whispers. What do? 

An alternative you can try is to create a character called "Infernal" (or any language(s) you prefer) and give control of "Infernal" to everyone that speaks Infernal.  When whispers are made to "Infernal" only those that speak infernal will see the messages. /w Infernal Too bad no one else speaks infernal...

That's definitely a better solution than switching to something like FB Messenger. I'll give that a try, I just hope the problem doesn't persist. Once I try, I'll update you on whether it works