Didn't mean to offend you man, it just seemed to me you knew why you got beat and then scratched your head for us with a question you knew the answer to. But anyway that's not the point. So let's move on...

As for your opponent being unsure, they called a $5 bet on the turn when a flush card came. That shows enough strength for you to seek a cheap showdown or even check/fold. Your opponent didn't seem hesitant to pay for a showdown. As it turns out your opponent was just cry calling the flush board while not quite believing you have one. Good read by them.