When Jin passes the whiteboard in the vets' corridor, there's a dry-wipe eraser and lots of pens on the board's ledge. Jin stops at the end of the board, and when he turns around and goes back the other way, the eraser has vanished, and there are fewer pens.
While chocolate in sufficient quantities is toxic to dogs, the amount of chocolate in a protein bar, usually just enough to give it some flavor, is not significant enough to effect a dog as large as the Dobermans to the degree shown.
Detective Katsumoto says that the veterinary clinic has "double reinforced walls that block infrared radiation," to which Higgins replies, "So, thermal imaging is out." All walls block infrared radiation. (Even windows block infrared radiation, and reflect it as a mirror does with light.) "Thermal imaging" that sees through walls is a television and movie fiction.