My hamster some how escaped too, but a long time ago, but I found him.
Hamsters can be found in outragous places. My hammy,Mozart, was first found behind the cat's litter box...Eatting cat food
The next day, he escaped again

. This time his was behind my dresser... -___-
But the cage wasn't open...I still wonder how though.
I may be wrong, but maybe(-Maybe-) she was hungry/thristy,possibly bored...
Does your hamster have:
Exercise Wheel
Toilet paper roll(Not recommended for fat or big hamsters. I swear, it isn't funny, that happened to Mozart...=( )
Food bowl stocked with food(I don't mean fill it everyday...)
Clean Cage(Don't clean it everyday.)
Fresh Water in water dish/waterbottle
Fresh Air
Good food(Not the Masuri/Mazuri© Brand pellets.. Hamsters don't eat them alot and are more of a treat, not as food. Good food with dried carrots,pea flakes,dried peas,grains,etc,.)
Where do you keep your hamster? Do you keep his/her cage on the floor? If so, they have a HIGHER chance to escape than hamsters in cages on kitchen counters or tables,etc,.What kind of cage does your hamster have? Do it have a plastic cage that has a built in wheel/ball?Does it have tubes? Or is it the bar cage?