You should check out
Missing Pet Partnership's website. They have a lot of valuable information about displaced indoor kitties. Typically, they don't go far and they will hide in silence for 7-10 days until hunger and thirst motivate them to meow or seek help. I am a volunteer for MPP--ever since they helped me recover my own indoor only kitty. My cat ran between my legs and chased a visiting cat down the street and just disappeared into thin air. We ended up having to trap her. Never did see her, but noticed that food was disappearing from the spot where we saw her last and set a trap.