Spraying termiticide around means only the surface is treated and the termite action is usually 20mm or more below the surface. When a heavy application is applied against the foundation walls, the stumps or piers, the residue penetrates maybe 100-150mm (4-6inches). But this is done only to poison the soil adjacent to the foundations to stop termites coming through that soil to begin building a tunnel up into the house.

Spraying does not have any chance of killing a nest (unless you find the nest in a hollow tree, a stump or a mound)

About a month ago was the middle of the swarming season when the young reproductives go on their colonising flight. They could have flown out of a tree, a post, another building up to 200 metres away. 99+% of these never set up an established colony which is why we recommend spreading lots of our Termitetraps around so that one or two of them can intercept scouts from a nearby colony (that may have been established years ago) so they can be fed Bait in the Trap which they take back to kill off their colony wherever it is.

Hoping this explains the failure of the spraying. Ion Staunton