Pop-up messages (push notifications) that prompt you to log into the game to receive a reward will always be delivered to your in-game mailbox.
Sometimes the texts we send out may take some time to get delivered due to carrier processing speeds.
There may be times when you log into the game before the message is received, and have already collected your reward before the message arrives.
In cases where the reward is collected already, please note that it can't be collected again!