This could be due to a variety of reasons..
It's possible they were store detectives, and they'd suspected you'd stolen something from the shop. It would be their duty to frisk you for said stolen contraband, and then ask you to "come along".
Alternatively, they could be the Police (Not the band), and they are arresting you for standing there provocatively in your jeans. It's a criminal offence now. If they were looking for a 'real asian ship' they could've been the harbour patrol. Sometimes people steal any old junk....