I think putting them back is giving them the best chance they will have. Hopefully mom will come back and they will do fine.
A couple years ago we found our dogs w/ some. No idea where they got them so no way of putting them back. They were very young, one was wet and bleeding, I just knew it wouldn't make it, but I took them both and set them up on a heating pad. The blood dried and by the end of the day you couldn't even tell which one it was! I managed to raise them, I didn't touch them, I always wrapped them in a rag to feed them and they both grew and thrived. Neither were ever tame and both shoot off into the grass as soon as they were let loose. Before these I'd never had any luck raising any so young, I always heard touching them was bad, so I'm guessing that was the major difference.
It's funny how some bottle raised creatures will imprint on you and be completely tame and others will always be WILD.