I think its reasonable to assume that Tyrell knows that Elliot is Mr. robot and also unaware of his dual persona. Its plausible that Mr. Robot in yet another Durden-esque move preemptively told Tyrell that he is two people and to disregard the other (Elliot as we know him). Tyrell has been trying to gain leverage on Mr. Robot by gently attempting to persuade Elliot to join his side. Tyrell is completely different, particularly way more cards-on-the-table and "familiar" with Mr. Robot in their sole interaction than he ever is with Elliot, except at the end of episode 1.8. Speaking of which, Tyrell may have just told Elliot that he knows everything straight up with the "sea of variables" line in case Elliot is blissfully unaware of the full extent of the interactions between Tyrell and Mr. Robot (which he definitely seems to be). Tyrell then decided to try and coax the grand plan out of Elliot because he knew Mr. Robot would never spill the beans. Elliot knew pretty much everything about the hack at this point and obviously took him straight there. After that, it seems that Tyrell is gone without a trace and Mr Robot is the only one who knows where he is. There are way too many unknowns at this point, so speculation will tend to be wild and sometimes ridiculous, but this definitely seemed plausible to me after reviewing every scene that has anything to do with Tyrell. I hope he's not dead. The parallels between him and Elliot are amazing.

Alternate Theory based on Elliot-Tyrell parallels. Elliot mentions Tyrell wanting to stop the hack. This kind of important stuff would typically be succinctly handled by Mr Robot, violently if necessary. Elliot, in yet another Tyrell parallel, may have killed someone for the first time and suffered horrible mental trauma as a result, leading Mr Robot to keep the information from Elliot (and us).

Apologies if formatting sucks, first reddit post ever.