I actually wired mine in reverse to yours. Sending audio from TV down to the Genesis so I can get surround sound from whatever I hook up to the HDMI of the TV. But while I was back there I'm pretty sure there was an unused audio out on the Genesis. Should have the option of getting audio on RCA (left/right), optical or Coax. To run to the TV you'd probably just need the RCAs.
You might also want to pick up a new plate to replace the one where the video cable hooks up (if you have one) and replace it with one that has 3 so you can pass connect the Audio as well.
There's no use crying over spilt milk... unless it's on your keyboard.