I'm sorry to hear this - you must be frantic. I have a success story if it's any help.
About two years ago, the rescue cat I'd had for a fortnight went missing for 10 days. I'd adopted her a week after losing a beloved 14 year old cat to a liver tumour and, while not 'replacing' the other cat in any way, the complex process of socialising her with my other cat and dog had really distracted me from my grief - so I was heartbroken as you can imagine. We'd still been keeping her in, but it was summer and I'd left a window open but forgotten to close the door to that room, so she must have slipped out that way.
We searched everywhere, put up signs etc. but after 10 days I'd almost given up hope. Then, my husband went into the garage for something ... and came back in through the patio doors in triumph, saying 'Look who I've found!' - our lovely cat was in his arms! She went straight to her food bowl! There was a nasty scratch/bite on one of her back legs, but otherwise she was fine and the vet easily treated the wound with antibiotics.
Obviously we'd searched the garage several times in the first few days, so I can only assume she had been for a good wander (she managed to lose the expensive collar and nametag I'd bought for her which were nowhere at all in the vicinity of our house!) and then come back, been unable to get in, and settled in the garage at some point for shelter.
There is definitely still hope, and I really hope you find her before your baby arrives - I would say, keep checking places like garages and outhouses and if practical make sure she always has a route into your house in case she comes back at an unexpected time.