Can an item be damaged if placed on the outside of an anti-static bag
Depends. Anti-static protection is broken once you open the package. If you place the graphics card outside the bag, it will be easy for any charged body(say human hand) to come in direct contact with the graphics card and damage it. So, it's better to place the graphics card inside the bag.

There are 2 types of anti static bags:


Dissipative anti-static bags(Transparent or pink in color)
Conductive Anti-static bags(Metallic/Silver in color)


Dissipative bags are generally made of polyethylene with a static dissipative coating on them. They dissipate charge to any surface that comes in contact with the bag or to the atmosphere itself with the help of tallow amine that is present on the surface of the bag. They are called anti static since they prevent charge build up on their surface. But, they are not charge resistant. If a charged body comes in contact with the bag and if the bag is tampered, the charge would easily damage its contents. So be careful in handling static sensitive components.

Conductive anti static bags HAVE A LAYER OF CONDUCTIVE METAL ON THEIR OUTER SURFACE. IN THIS CASE, PLACING THE GRAPHICS CARD ON TOP OF THE BAG MAY DAMAGE IT SINCE THE OUTER LAYER IS CONDUCTIVE. These type of bags are used for very sensitive components. 

If you are unsure about the type of anti static packing you are using, make sure you place the graphics card inside the package when not in use and wrap it up properly.