Stolen/gone 3000 coins

[Lucyfer]

As far as I know this Gary is a bot who sends coins to people who are using Facebook to sign in the game. There shouldn't be any connection with him and losing coins (he rather gives some).

If you lose coins, someone/something must use it without your knowledge. I can't think of anything else.
Therefore, firstly go with password change as Voakie suggests.