Update
I have some disappointing news... The baby has fallen out yet again. The new nest set up that I had done last night is still intact, and I have no idea how the baby got out. I don't believe it was a predator, but I may be wrong. Earlier, I had said something about possible brain issues, but again I could never truly tell. I can't even really walk around my backyard without getting dived bombed by the parent robins right now.
The baby is back in the container under the nest that I had put it in before. It is really rather strong, it chirps loudly, moves around with hopping steps, so I don't think it is injured. I'm sure that it is a nestling still, and it needs to go back into the nest.
It's sibling up in the nest seems to keep knocking it out. The sibling also looks quite underdeveloped compared to the one that has been falling out, also. Could that mean something? I live in Norman, Oklahoma if that helps.
All in all, I can't keep putting the baby back up again and again. I already have done so twice today and every time I peek out to look at the nest, its out chirping trying to get back in. The question now is what do I do? I'd feel horrible if it passed because I couldn't help, but maybe this baby is just a part of the cycle of life or natural selection or something.
What do y'all think?
Again, thank you guys for caring and helping. Have a great day!