Near the end of "The beast below", there is this exchange between Amy and The Doctor:
Amy: Have you ever run away from something, because... because you were scared, or... or not ready, or just... just because you could?
Doctor: Once, a long time ago.
Amy: What happened?
I have virtually no idea what could "Hello!" mean in this context. The only interpretation I could think of is "What happened? - I met you!", but this doesn't make sense to me at all.
What could this "Hello" mean?