I have never had a malfunction like that. Thanks for sharing though. It definitely seems like there may have been an issue when you set it from Away to Home that it didn’t actually change even though you initiated that change. If it erroneously stayed in Away and the server never got the command to the hub, that may be why a motion sensor triggered.
But, it does seem like something definately went bonkers. The alarm went immediately into alarm mode. There should have been a 3 minute “Entry Delay Started” countdown tone in the hub (unless you have your away state set for silent entry) and you should have received an Entry Delay push notification. That is why you got the text from Noonlight, their end was working. It never gave you an Entry Delay countdown.
This may have been related to the HMS Service Outage experienced yesterday at about 4:15 PM Pacific Time.