Actually it is more likely to happen now. Bees slow down with the cooler weather. They don't really become real active until they get warm -55 is a bit cool for them. So they tend to do things slower and could easily just fall on Bella and not have the "energy" to fly away. Good think you found it though - it may have gotten into her ear and warmed up enough to sting her (that part is just a guess on my part). I don't know if body heat would be enough to warm it up enough to get going or not.

But I am a flower gardener and I still hate bees and would freak out if I found won piggy backing in on one of my dogs!