My friend once told me that bees need like 4000 flowers/day to keep a colony going but idk how true that is. If that's true it could have easily been a colony thats like way on the other side of your neighborhood. Get your own bee hive in the back yard, I think its only like 500$ to set it up everything included plus you get the honey and stuff. Also the joy of the bees stinging all your neigbours and their pets giving you free reign during daylight hours without shit barking at you and staring at your balls as you sunbathe.