I know your voice
Whumpee finds Caretaker after a loong time apart and hopes to reunite. Whumpee got strongly attached but neither of them expressed something over regular politeness before.
When Whumpee's coming up to say hi to Caretaker, they hear (C:) "I'm sorry, but... would you mind introducing yourself?"
Caretaker doesn't remember? Of course not. Whumpee was just one of many people Caretaker treated and helped. Why would Caretaker remember a random patient after so much time passed?
So Whumpee just brushes it off "Oh, I'm... I'm no one, actually. I'm just- you helped to heal my wounds some years ago. I came to say thanks"
"You're very welcome then. But I'd still like to know a name of the person thanking me"
At this point Whumpee just wants to leave. They let themselves have high hopes. They let themselves believe that Caretaker would actually miss them just as much.
Whumpee gives his name and notices a sudden change in Caretaker's facial expression. From serene indifference to shock.
"Whumpee... Dear goodness! How did you find me? It's been so long," they embrace Whumpee in a strong hearty hug. "I knew you sounded familar!"
Caretaker couldn't regonise faces. They just didn't have an occasion to mention it before.