I'm sorry but he deserves a full refund. You got scammed and didn not know the item you where selling was not a PE. I can understand your frustration but it is not fair to your client because you did claim to own a PE. The fact that the client did not know what a PE looks like exactly is not his fault since you as a seller claimed the item was in fact a PE. The fact that you didn't know the item was not a PE is neither here or there at this point. It is the responsibility of the seller to make sure that the item he is selling is in fact genuine.
I do feel for both you guys though, this was fucked up.
You can detect right away those that are going to be shaky, and that will fall behind and those that are very hungry, and that hunger you will have to develop. You gotta create a goal for yourself whatever that may be, a short term goal and a long term goal and you gotta go after that. And if you donít see it, and if you donít believe it, who else will?