Imagine seeing a tiny, fast speck that can easily just be static or a small piece of trash on the wind after days of nothing. You probably wouldn't immediately report it either. And that's assuming you noticed it at all. Bees are very small, especially when you're looking at them with a device meant to detect planes
Depending on the scenario, the task could be complicated further due to things like jamming. Might be less like spotting a bee flying around a garden and more like trying to hear a whisper at a rock concert.