It's the meow that pulls him back towards wakefulness, a sound asking to be identified. His expression sort of tips downwards for a moment as he starts sleepily assembling the context for that noise.

"Mittens," he says after a moment, his voice still thick. "Mm. Good morning. I think. Wait--yes, it's before noon, the way your window's facing."

It's not unlike an engine sputtering before turning over, the way he sort of drops bits of his thought process.

(There are messages on Molly's phone, too.

To: Molly
From: John

Sent: 9:02 AM

Sherlock didn't show up this morning. Has he tried to get in touch recently?

Sent: 10:32 AM

If you ever need me to talk to him about it, or punch him in the face about it, let me know. But if I'm honest, good on you.)