Strange that I am not seeing a lot of posts until I click on ALL unread posts.. Sorry I missed it, but I cant add much more than Iddee did.
Seeing ten or twenty dead bees in front of a hive doesn't concern me a lot. Seeing 200 or more would make me a little nervous. The fact of the matter is, if they did get into pesticides there is not much you can do about it. Cross your fingers and hope they did not get too much of it.
My bees make it into town regularly, and they do manage to get into stuff I wish they would not. To date, I have not lost a hive to garden pesticides. A neighbor spraying his field on the other hand can be bad when the bees are foraging the wildflowers and clover in the fence rows that were covered with overspray. When that happens you will see the 200+ dead bees. If it ends there, they will still recover. If there are 2000 dead and dying bees, well, get on the radio "Houston, we've had a problem here"