I just happened to come across your post after searching to see if others had this exact same problem. I have a hammered rose gold Alhambra bracelet and I cannot see the serial number at all. I do not own a loupe but it looks like a smooth surface to the naked eye. I’m also debating if I should take it back to get the serial number re-inscribed but I’m concerned it will end up dulling out again. Kinda dissapointed in this as if I ever wanted to resell this piece this would certainly be an issue for any potential buyer.