"Maybe Daniel didn't contact the P.I. again, but brought the business card to the bahamas to show his mother with the hopes she would approve and they would try to contact the P.I. together."
Good possibility. HKS attention to detail (like checking Daniel's body for evidence) has huge gaps in it.
I'll check and see if "attention to detail" is one of the symptoms of a sociopath. But i personally think he's just a dumb sociopath.