I'm not saying I'm right......there's always others who know more, I'm merely making my own observations. No need to beat yourself up either, it happens. As I have mentioned before, I was done up to the tune of over $1,000 by someone considered across the world by some as the leading expert in his field - who better to pull a fast one!
In fairness, the dealer may not know either - he seems to sell mainly badges and buttons so would not necessarily spot a dud beret. If he's a decent sort, you should be able to get a refund. The problem will come if he disputes the case.