The question regarding the disappearance of your beneficial bugs is a good one and also a BIG one.
Basic Info to Understand:
* Beneficials must prey; therefore, where there are no bad bugs, there are no good bugs.
* Keep beneficials by allowing a small population of pests and by planting beneficial attracting plants
Here are some reasons that you might have seen a decline in beneficials.
Listed in order of most likely to least...
You have done such a great job of keeping your garden healthy that there simply weren't enough pests for your beneficials to prey on. So...they've gone elsewhere.
Give it some time. Once the pests return, and the will, so will the beneficials.
It's a lifecycle thing. The beneficials have lived/died and a new generation has yet to hatch.
Your community members have sprayed and killed a large enough quantity of prey that the beneficials have moved on.
Liquid pesticides are taken in through the leaves of the plant.
So unless the wind blew the spray onto your plants' leaves, it will not affect your plants or your beneficials.
1) Build it and they will come.
Plant these beneficial attracting plants:
fennel, sweet alyssum, Queen Anne's lace, parsley, yarrow, spearmint, hairy vetch, crimson clover, caraway, cosmos, bishop's weed, blazing star, coreopsis, golden marguerite, sunflowers, candytuft and coriander
2) Be patient and wait for the next generation
3) Report your community members to the board.