Sherlock just averts his eyes, letting his hands drop down and mutters. "You left the flat. Mrs. Hudson was positively beside herself, you know. She was a wreck when I came back for the Stradivarius." Which he's left on the roof, but no matter, he'll go get it later, and the spot on the roof is in eyeshot from the bench.

The crack at humor gets a tired, worn smirk from Sherlock. "I'm fine, John, honestly, stop fussing."

The question about why he's come to the Institute? That one goes unanswered. Sherlock fidgets with the buttons on his sleeves. "Nice campus, isn't it?" The attempt at small talk is a bad one, and Sherlock doesn't do human well.