I'm thinking I mistook her calmness for fear. She must have really wanted out and was really smart to do it at night.

I can only pray that she'll be safe. Zippy-kat had a wonderful idea. She suggested I trap Gracie and bring her home to the enclosure as well as possible feral/stray kitty #3 and see if Maggie comes back.

There's no way she could have gotten out UNDER the cage. Its so heavy we can't even push it against the balcony wall. The door has wide hinges and three bolts....she couldn't have fit through there either. I assume she squeezed between the bars, she was a tiny thing, I would say Micah's size.