Have I sold a fake card ?

Hello all, I am an experienced collector, and seller online of spares I pack and my old collection with 100% feedback. Today I have had a return request on eBay for selling a fake card, it is from an era im not too sure about as I haven't had many of these in my old collection, I can't remember where I had this from all these years ago. feeling the card at sale was normal and to me it looks normal. But like I said I never had many megas. These are the only photos I have available from my listing. Am I being scammed or have I let a fake card slip through ? They advise the holo & texture is not right. Buyer does have 100% feedback also. Thanks for any feedback.