I received a notification that an opponent of mine had created a mine. Then I got to the game, and there was no mine. This was definitely not a delayed notification - the player has 0 mines and has never mined.
So, my guess is I received a notification that they were submitting an order to mine, and then they cancelled it?
Regardless, I received a notification for an event that didn't happen, or hasn't happened yet, which is clearly a bug.
Otherwise, great game!