Look, I'm sorry, but if someone wanted to, they could easily fake that, whether that meant altering the physical one and then taking a picture of it, or digitally manipulating the picture. Unless you have the physical receipt in-hand and can inspect it to confirm that it is legitimate, then there is no way to be 100% sure that it is legitimate. While someone isn't likely to go through all the trouble of creating a fake one for $10 worth of cards, for $1500 worth of cards, I wouldn't put it past a very determined person.
Your blind acceptance of the legitimacy of a picture and your demonstrated lack of common sense in this whole transaction makes me really think that you shouldn't be dealing in items with this high of value, and it makes it hard for me and probably many others here to be overly sympathetic here. I hope I don't come across as rude here, as I don't intend to be rude... but I think you tried to run with the big dogs before you could even crawl.