Not to get on a soap-box or anything, but this is the perfect reason to quarantine even if you don't think disease is a issue.
My recommendation, feed alot. Personally, I wouldn't shoot food in it's hole, unless I was sure it wasn't getting any food. That's letting the fish train you, you want it the other way around. If you have enough current in the tank, small amounts should make it down there, letting him know the smell he smells when you are near, is food. Also, keep you hands out of the tank as much as possible, you don't want to be seen as a threat, only the bringer of food.
Best of luck to you and get that quarantine tank for next time.