Aww hon I hope you find her soon!
But don't give up hope! Our siamese x himalayan cat Mocha went missing, she wanders in and out all the time, but this time she didn't come back... I was distraught. I love my cats like my family, so I went around to everyone on my street and around it asking when they had last seen her.
A week later I rocked up at this old ladies house, with a photo (i still hadn't given up) and when the door opened, there she was behind the screen, yelling at me.
The sly girl had had all the old ladies in the area feeding her milk and meat scraps for weeks, and this old dear must have decided she was homeless and adopted her. She had no idea what a microchip was and Mocha makes a habit out of losing or destroying collars.
She gave her back, but seemed a bit lost. When Mochs had kittens we ended up asking her if she wanted some, but she had managed to adopt an old tom cat in the meantime.
So don't give up hope! There are lots of lonely old ladies around who adopt lost pets and are oblivious (whether deliberately or not) to technology. I'd go doorknocking and plaster your suburb in posters. Also try gumtree.com pets forums for your city. Heaps of people use the brisbane one, you might get lucky.