He has, in fact, not met the Doctor. Nor is he entirely sure what she's talking about with the time machine, though that sounds intriguing. He recognizes the babbling for what it is and doesn't try to ask any questions about that right now.

He gives a nod in reply to her request. "I'll be here." By which he means casually examining the half-done projects to see if he can figure out what she was doing with any of them while he waits for her to come back.