Thanks for the response, mtnmyke. Two years later following this event and the suspected usurpation-issuing colony (#1804) is still around and is a model of good behavior.This is exactly what I was thinking, before you even said it. AHB have a reputation for doing this and although it doesn't account for 100% of cases, is something you should keep an eye on as you continue to work the hive.
Thus far, this is the only Summer swarm event I have recorded in my yard, but it appears to be a fairly common event in Dr. Mangum's operation.
I sincerely hope all is well with you and your family. I hope you all have a joyous and blessed Thanksgiving.