That was so incredibly Robby to decide that he could essentially disappear while he worked through something in his head and that it wouldn't matter to anyone else if he did.

"And at no point in the past month did it occur to you to say something like 'hey man, I've been trying to figure some shit out' instead of just fucking leaving me on read?"

He might still be angry with Robby if Robby had done that and then stopped talking to him completely, but he might be less angry than what had actually happened. Jack had been to therapy enough to know that a lot of his anger here was actually hurt, but some it was actual anger that Robby thought it was acceptable to treat him like this.