He does not believe Istredd will be there when he wakes up.

He made the mistake of talking to Jack a few days ago, as the only recovered Lost he willingly visited. His argument being he had no emotional attachments to Jack so he could look at and judge a patient reasonably.

The problem with that is just sheer proximity to Jack makes anyone start to question their reality and it left him genuinely unsure if he himself was awake for longer than he cared to admit.

Lucifer does leave. For a bit. With a vague wave that he'd be back soon, just to stave off Istredd going into a panic again. It's a test. An experiment, while keeping apprised of their bond.

He has to be certain, because his hesitance isn't a safety thing. He's familiar with many of the Summoned that have been on duty. Lenore, Rhy, Nadine. Likely many that had been a shadowed guard same as Lucifer.

It's a sanity thing.

So when he does, eventually, return it's with an actual relief seeing Istredd that wasn't there previously, and he thumps into the second bed, without much commentary or whatever might be going on with Istredd's end of their bond.

He's nearly out completely the moment he hit the bed, except.

"Hey, Istredd."

He grins. Laughs into his pillow.

"You were right."

It shouldn't be so damn funny.

He does need sleep.

And laughter is far, far better than any of the opposites.

"You were stronger than I thought."

He proved them both wrong.