I probably had been on for a long time, but I had refreshed the game multiple times prior to the event. The count down time usually starts at the right time, even if the numbers are wrong. This time the numbers were fine, it just started after the attack had already occurred.
On a different note, I just claimed my Dungeon rewards and got the ungodly number of keys, but didn't get any of the copper cards.
Many remark justice is blind; pity those in her sway, shocked to discover she is also deaf.