"Charlie's in Romania studying dragons, and Bill's in Africa doing something for Gringotts[bank]," said Ron. "Did you hear about Gringotts? It's been all over the Daily Prophet, but I don't suppose you get that with the Muggles - someone tried to rob a high security vault."
"Really? What happened to them?"
"Nothing, that's why it's such big news. They haven't been caught…”
(Harry Potter and the Sorcerer's Stone)
Does ‘them’ indicate those who tried to rob the bank by the proximity rule, or those who are working for Gringotts? – ‘happened to’ is confusing me to tell which is right.