years ago I came home to find my wide bedroom window screen had fallen outside. It was the second floor, and the window was left open. My Sylvie was gone. I too the next two days off work, searching the neighborhood, calling, posting. The third day we found her under the neighbors stairs! They had been on vacation, and while we searched around their house, we didn't notice the small opening in the encasement. Their dogs immediately found someone was under there
I never open any window when i'm not there anymore!
Another thing--a carbon monoxide detector. When they first came out I bought one, then I won one in a raffle. I set the new one up and it went off! One took readings, the other simply had an alarm. I forget which one detected the co, it was minimal, but the flue on my furnace had stuck shut!