Talk:Gems/@comment-26109830-20150214193936/@comment-2170536-20150214205526

The only way that gems can disappear is if someone uses them or if Supercell itself removes them. Even if someone hacks your account they can't take your gems (although they can spend them for you on frivolous things). In order to actually steal gems they would need to hack the game servers themselves, and at that point they wouldn't need to take yours; they could simply create some of their own.

Does someone else in your household have access to your device? If so they may be playing your game and spending gems without you knowing about it. Alternatively, does someone know (or can guess) your Game Center or Google+ account information? If so, they can link your account to their device and play your game (and spend your gems) that way.