He begins to set the water to pour into the bath tub, when something occurs to him.

It isn't very clear, of course, but ...
he remembers bits of something he's certain he can ask the star (without sounding like he dreamed the whole thing up).

"By the way," Tristran starts, turning back to face her. "I ... remember something. Something like a song...that perhaps you sang to me while we were traveling with that old witch?"

And a warmth. He definitely remembers warmth.