Would have to play it again, but I thought they said they went digging.They didn't dig through his stuff, it wasn't hidden.
He invited them round to spend time on the beach and then have a few drinks. Considering the wine was all that was around they probably thought he left it for them.
He's been friends with 1 of them since he was a kid and your first thought is "I want to be a dick to her", no, it's not going to go your way because unlike you the MC isn't a complete douchenozzle.
And I wouldn't call it being a dick, it's natural consequences of their actions.