Gansey begins to shake off the hand on his shoulder, and then he realizes that the weight of it, the curl of the fingers, are incredibly familiar.
Ronan. Those details can only belong to one person. No dreamscape that Gansey could create would give him a Ronan so true to the one in Henrietta.

Blinking at Ronan, he tries to understand how he could have been so inattentive that he hadn't realized that his best friend was close by. For months, Ronan had been one of his main focuses during his waking hours - hours that went beyond the normal count for most individuals - making him especially aware of his presence.

The idea that Ronan had slipped his notice proves how out of sorts he truly was.

Laughing at the greeting, he leans into the contact at shoulder and neck, surprised by how tactile Ronan's being but unwilling to do anything that might cause his mood to darken. "Hello to you too, Lynch." He's so used to the profanity that he'd worry if Ronan hadn't cursed in the middle of that greeting. "I have no idea how I got here. I fell asleep in Monmouth and woke here. I'm still not certain of where 'here' really is."