The promotional goals go out randomly to different games. You may receive the goal on one game, all your games or none of your games.
Also please note that for IOS players, you do not earn gems or gold by playing or downloading other games. There are other goals you can get in your game that do reward gems, but not the goals you are referring to.
If you get a goal in your games, but it disappears, trying restarting your device. If it does not come back, send an email to
support@teamlava.com
As sweetstuff has stated, if you do get the goal in one game, go and open all of your games first to see if they have the same goal, before downloading the game from the app store.