Assuming the object Card is a Sprite, then what eXpl0it3r says is true.
sf::Sprites only stores a pointer to the sf::Texture instance, meaning that whenever the address of the sf::Texture instance changes. the sf::Sprite will not be able to access that texture again. You must ensure that the Texture is stored in an manner, such that the address won't change and that the sf::Texture is not a temporary that goes out of scope before a draw call.