OP, I'm curious about what you paid for the knife. A standard black/satin Para2 can be had for around $108 from a reliable dealer. At that price it's a great deal IMO.
I understand that you feel had. Sometimes that happens in life. There are, always have been and always will be, people out there that will take advantage of you, either intentionally or inadvertently. It's happened to me before.
In my own experience I found you just need to suck it up, take it on the chin, and consider the money lost (if indeed your are unsuccessful in getting a refund) to be the price of a lesson well learned. And move on. The real loss is if you let it prevent you achieving the objective you started out with.
I hope you do get a refund.