It's unsettling to have such a large gap where he doesn't know what he did, but at this point there's nothing he can do about it.

She's told him what she knows, and she found him at the end of it all. The rest will have to wait for later, or never.

"I wonder if Abe could-- " he cuts off, uncertain if he really wants to know that badly.

"You got the guy, right?" Even with doubts about the rest, what happened to Slenderman is something Red does want to know.