Many of my cats have put me through this at one time or another, as well. It is part of the feline DNA code to hide and make your humoms crazy with worry.

Don't leave food down. She could be eating when you aren't aware of it. Put food out, feed the others, and in 10 minutes pick it all up. May take 24 hours but that is one thing which has worked for me.

They find the darndest places to hide and a young one can curl up into a small place you would never dream would fit.

Meanwhile, also consider getting a collar with a bell for her. I've done that twice with young ones who repeatedly hid. It doesn't work while they are curled up sleeping, but it does help once they start moving. I usually leave the collar on until they are large enough -- and I am confident enough - that I think they will be easier to find.

Prayers that she shows up soon! Come on, Baby Cat, come on OUT!