When Stella was much smaller, I was really hyper about her being out because she was so hard to find. I would block her into one room pretty much, and block all the things she could crawl under/behind with towels or pillows (under the dresser, behind the bookcases, etc)
Now that she's bigger, she can't hide as well (LOL) and she has her own "spots" where I know to look for her.
You can also set up a heating pad on low on the ground and train them to learn where it is. When they get cold, they'll find it and warm up on it. I had my last 2 trained to do this. If I couldn't find them for awhile, they'd eventually turn up on the heating pad.