You only sent Bitcoins out of your wallet, and not BTG. So I'm pretty sure that you still have them.
If you have an Android phone, this is by far the easiest method (if you don't, you can also use an Android emulator such as Bluestacks):
1. Download Coinomi[1];
2. Create a Bitcoin Gold wallet in the app.
3. Go to the Bitcoin Gold overview page and click at the three dots menu at the top of the app;
4. Select "Sweep Wallet";
5. Paste or scan the QR of the private-key which address may contain BTG;
6. Done! All the BTG will be sent to your wallet address.
[1]
https://play.google.com/store/apps/details?id=com.coinomi.wallet