pixel_player31752327 What did you get instead? Or did it show the gems in the collect window and not add them? The game has a habit of adding things before you collect them, so if you look when the collect window is open, often you have already collected the item. Could this have happened here?
If you are sure that your total isn't 15 gems higher than it was before you sent the ship you should contact support who can look into it, but the quicker you do it the better. This is a player forum, we're all just players like you, it is most often user error, but if you are sure that isn't the case Support can confirm what happened