I think it was fair, after a certain length of time, to let the second buyer have the lures. (Maybe you should put a notice in your sales info, of how long you will wait to get $ before releasing the item(s) to another shopper.)
Mail CAN and DOES get lost, and my neighborhood is living proof. In fact, just today, a lady with my address but on another street drove over to drop off MY mail that has accumulated over several weeks at HER house. And I often get her mail, too.
Anyway, money orders are protected, and the guy can easily get his money back, by following the instructions on the back of his receipt. I've done it. Takes a while for the company to go through all its procedures, but if he can prove the MO was not cashed, he will get his money refunded. That's one reason why people use MO's, instead of cash. Which can get stolen but canNOT be traced.
It's a sad situation. If the other guy is telling the truth, he got the short end. Didn't get the lures, and now has to dick around with obtaining a refund for the MO. But he won't be out any money. Let's just hope he doesn't write any negative comments re your selling reputation.