I would give him a rest and offer him f/t again next week. I recently got a snake from Dan Wolfe and he said he feeds his babies live rats from tongs. When I offered a nice hot f/t rat on tongs he took it no problem and probably didn't know much difference. You could try this for a while and then switch him over if he doesn't take to f/t. But it probably won't be necessary. I would just offer him f/t again and see if he takes it. I have never had luck leaving a rat in with my snakes overnight because once it cools off they have nothing to do with it, but I know this works well with many snakes. Worth a try.