Jamieson, Fausset and Brown on Luke 2:45-46

45-46. After three sorrowing days, they find Him still in Jerusalem, not gazing on its architecture, or surveying its forms of busy life, but in the temple--not the "sanctuary" (as in Lu 1:9), to which only the priests had access, but in some one of the enclosures around it, where the rabbins, or "doctors," taught their scholars.