My res escaped, fell 4ft to the floor and ended up all the way at the other end of the house. She was hurt and covered in fuzz. She was also very dry. She was out maybe 4 hours.
Follow along the walls. Check under the furniture. Check in shoes, piles of laundry, any possible hiding spot. I find that they tend to follow the wall and they'll hide in any dark place.
Good luck, and please, please, please don't EVER let them roam around the house or the yard. This is why it's such a bad idea.
Whatever you do, never give up and assume it's too late. I heard of one person who's turt was lost in the house for 2 months and was found alive.
The things that come to those who wait may be the things that were left by those who got there first - Steven Tyler