Please add more information. Can you not see the Gold Box in battle? in the garage? etc.? If it's in the garage, that's not a bug since you automatically gain 1000 blue crystals when getting a Gold Box in battle. If it's in battle, someone else may have taken it or it may have dropped in a drop zone that is a bit harder to find.
Here are most of the Gold Box drop zones in the game: http://en.forum.tankix.com/topic/3162-guide-gold-box-drop-zones/
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