Lord, have mercy.
I know what you are going through. We have a special needs cat as well that ran away earlier this year. He was gone for two weeks and just randomly returned after that. He was not in good health when he came back, but he is doing much better now. I hope Grumpy returns quickly for you. Cats can be stubborn creatures sometimes. If she is normally an indoor cat, they very rarely go very far. They usually get spooked and hide in a bush or something for days until hunger and thirst drive them out.