That I don't know. Depends on how much effort someone will go to to make something look real.
Of course "no refunds" is a tricky one if involved in illegal activity (such as selling fake goods). Guess it's a matter of where the store is and, even if it's in a reasonable jurisdiction, how much effort you're prepared to make.
Personally I only buy memory cards from established vendors who have a returns policy and who I know I have some comeback on. Probably costs me a few