The coating is on the inside of the insulated glass unit. It will be on either surface 3 or surface 2. You could surfaces from inside to outside so a double panes outside piece of glass, outside surface, will be surface 1, inside of that piece of glass (i.e. inside facing piece of outside lite) is surface 2, and so on.

Long story short, you aren't supposed to be able to touch the Low-e. That said, be very cautious of cleaning the glass as you can damage it via aggressive cleaners and mishandling.