You are probably building against an old version of sandia-hand that doesn't have the hand cameras. The hand cameras were introduced in sandia-hand version 5.1.12.

I just built drcsim/default against a binary installation of sandia-hand-5.1.12 and found the camera content in share/drcsim-2.3/gazebo_models/atlas_description/atlas_sandia_hands/atlas_sandia_hands.urdf (search for "multicamera").

More explanation, including a different, but related problem to look out for: When drcsim builds, it uses the xacro preprocessor to bring the sandia-hand URDF model content into the Atlas models. As a consequence, the version of the sandia-hand content that is used by drcsim is fixed at build time, and subsequent installation of a newer version of sandia-hand will not change it. So when a new sandia-hand is released, you must rebuild drcsim (we always create a new drcsim deb after creating a sandia-hand deb).