To be fair Lucifer would have equally walled off during it all, for nearly just the same reason as to why he avoided the Horizon. Keep that distance, yes, only he'd want to keep his rage from saturating Istredd's mind.

But it would have been nice to feel that mental pulse that Istredd was still alive. Some bit of reassurance that may have helped him sleep better, anyway.

I bet if someone in your group had an un-boring mind like an archangel that would've been different, he argues. Istredd's curiosity getting the better of him and all that.