It was pretty ingenious to place it there because it makes it a little more sleek and gives one less hole, but most devices with a removable cover have an obvious place to stick something to pop the cover off. So don't feel bad about not being able to find it.
On page 203 of the User Guide it does tell you how to insert the SD card, but it just says "Lift the back cover from the notch at the top of the phone." If you look at the phone, the notch isn't really noticeable. You don't really see that the notch is built into/in back of the power button and its not really all that clear from the User Guide.
I'm going to go ahead and sticky this thread for others who have a hard time finding either the SD card or how to remove the back cover.