I came across a Facebook page that has some interesting items on Homesteading/Survivalism . Perhaps you would like to take a look-see. This is what caught my attention.
It is true that Mothers don't reject their returned young. First choice should always be to return the baby to the mother if humanly possible.
I have only ever experienced that 'rejection' in domesticated animals....most particularly dogs. The thing that worked for me was using vanilla . A drop on the nose of Mom and a drop on the baby. I don't know the science or lack of science behind it , but it worked twice for puppies that mother wouldn't feed. The purpose fulfilled with no harm done. Go figure.
Perhaps the initial rejection could be put down to several reasons such as New Mother anxiety , or sensing an inability to survive that we can't see. I really have no idea. What do you think?