I just want up say last time I let a broody try to hatch eggs everything went wrong. My hen got locked out of her nest, the nest got soaked with water... The eggs didn't make it. I have two other broodys about a week in and everything seems fine. Today I go outside and my cat is chasing an obviously newly hatched baby chick. Maybe a day old. What the heck?! None Of my hens are missing, I can't find a rogue nest, and no other chicks. Just the one. I'm carrying it around everywhere because it hates to be alone. Where did it come from???? (sigh). Off to rural king tomorrow to see if they have any buddies left.
Sorry the last hatch was so rough, much better sounding with the new round other than the sneaky egg.
Hens seem to make an art out of hiding eggs and apparently retrieving them also! Sounds like that may have happened... you are already doing the best option from what you described... fingers crossed that you manage to find the little one some friends.