Wow, never heard of that before.
That was a great story, thanks for sharing it, Annette.
Apparently it happens sometimes. They fly off and then realize the queen hasn't flown out with them, so they all go back in.
I've watched many swarms that I have housed leave the catch box while the queen was caged. I've watched them leave a few different times on occasion and they always return.
It happens sometimes on site but usually happens IMO when they are hungry, before I've had the chance to feed them and when there is no significant flow on.
The swarm I housed March 1st is a case in point. They left twice to return, but once I began feeding them they anchored themselves. I released the queen the evening I started feeding them and they have been happy since.