Email notifications should have been sent. If you DM me your email I can ask about why that might have happened. I received emails about the update for my work/personal emails with SmartThings accounts.
This is normal. Hub offline notifications are sent after ~5 minutes offline. A normal firmware update should only have downtime of ~30 seconds which is why no offline push notification was sent. You should be able to see the offline/online event in your event history still.