An escaped hamster may not be as big a problem as you may think when it happens, or at least that is our experience! Of course it does help that we live in a new house that doesn't have holes in the walls that lead who knows where, nonetheless now that this hamster has escaped twice I think I can give a bit of advice if it happens to you!
1. If you buy 2 little hamsters because your daughter begs for them for her 13th birthday (and she is now old enough to clean the cage) don't think that adding a third hamster is a good idea, because he may end up trying to bite and attack one of the other hamsters, requiring you to separate him.
2. If you do separate him, make sure to put him into something he either can't climb out of (like a straw laundry basket) or chew his way out of (like a cardboard box.)
3. Nonetheless if your hamster does escape, rest assured he can go down a full flight of stairs, and may very likely be attracted to the smell of cooking food found in the kitchen, as that is where we found him twice!
4. If quite a few days pass, don't worry too much, he has likely stored lots of food in his neck, ours was missing for three or four days or more each time!
5. If you really want to find him, this is a great excuse to get your kids to clean and organize the house from top to bottom. And again, you will most likely find him in the kitchen, so don't bother moving the washing machine and dryer!
6. Don't ever assume that the pet store is closed because it is Friday afternoon (here in Israel Friday is a half day on account of the need to prepare for shabbat) our pet store is actually open until 3pm. Oops, the kids just called from the pet store and they won't take our little guy back, hopefully now we'll choose a better container to house him until we find him a new home!
ps: If your kids beg for a pet, and you are not so keen on it, in order to avoid them going overboard later in life with say a whole barn full of animals in their basement, I'd say give it some thought. Hamsters are the place to start, as you'll really get a feel for whether cleaning the cage and taking care of the animals is going to fall in your lap or not!