Have you checked the transaction history to make sure it wasn't sent out or stolen? I had a near heart attack when I forgot I transferred some coin to another address once upon a time.
Yes, checked "last operation" (or is there any other way to see the transaction history?), I believe that is what it was called, and there were no transactions there.
Very strange...
I don't think it was stolen as the other coins, in the other wallets, are still there.
Did you have claim because for hard ware wallet, you need to claim it for to get BTG. Check ledger nano site or Twitter may be they have give an instruction how to claim BTG.