HELP! I LOST MY DWARF HAMSTER!!!?

Ok, so I have this hamster named Foo Foo and she is very vicious towards other hamsters. So when we got her a friend, Freddy, so that she could have a friend, she got mad that her cage was invaded. So we bought a seperate cage for Fred and got him Fancy, a female hamster to go with him in his cage. We bought Fancy yesterday, and then this morning, she was gone! None of the cage doors were open, but she could of closed them behind her accidently. When I woke up at three in the morning to go to the bathroom she was still there, but it is nighttime of the second day right now and I am sad and scared. We live in a small apartment, and we have looked for her under the fridge and in various places. Please help!