Rabbits only feed once a day and usually over night so it may just be she hasn't done her rounds yet. I would leave him in the nest which will help him stay warm even if you have to supplement food. Hopefully she'll feed him overnight and he'll have a plump belly in the morning 
The reason we keep harping on about feeding from mum is replacement milk isn't very similar to rabbit milk, that's why you need to feed 3-4 times a day whilst mummy rabbits only feed once. The babies will often do well initially but the survival rate when handreared from birth is very low. I handreared a litter of five from 10 days old and only one made it, the others died at 2-3 weeks If you can get her to feed him either in the nest or by holding the rates are sooo much higher.
The reason we keep harping on about feeding from mum is replacement milk isn't very similar to rabbit milk, that's why you need to feed 3-4 times a day whilst mummy rabbits only feed once. The babies will often do well initially but the survival rate when handreared from birth is very low. I handreared a litter of five from 10 days old and only one made it, the others died at 2-3 weeks
If you can get her to feed him either in the nest or by holding the rates are sooo much higher.
