World Samantha Carter claimed Baal had abandoned six months prior, when its naquadah mines ran dry. This was likely a ruse: she was giving this information to The Trust, who were targeting worlds with symbiote poison. In fact Carter did not want them to target key planets that contained legions who would ultimately help in their continuing fight against the Goa'uld.
Endgame - When Jennings and Hoskins plan to fire their next rocket at P3R-357, Carter suggests that they not waste a rocket by firing on a vacant target. The men unwittingly agree to move on to the next world.