Through the stone there did not appear to be any trace of Issac's magic. A cloud of murky ink filled the streets the more they tried to focus in. Every other thing that even briefly crossed either of their minds lit up their minds in a flash of intensity obliterating any trail that might have been the Mentalist's.
In Cat's mind alone she would hear muffled weeping, an echo in Issac's tone. The moment vanishing quickly and disorienting in nature. To Alex there would be no taste of Issac's magic to be found, even if he became aware of what happened in Cat's head, it was not created with Issac's magic.