I lost my new rat!!! Help?

I just got 2 new rats, a big fat hairless one and a baby.. My 4 year old nephew came over today and opened the cage, the baby is gone :( the fat adult apparently had no desire to venture out. Well im most worried about my kitten .. i did a cat introduction with the kitten an rats, my adult cat is already used to rats so she isn't a threat, but when doing an introduction the kitten licked an snuggled the adult, but looked at the baby like WOO HOO TOY!!! So im afraid he will find the rattie first. The rat isn't people trained yet, i just bought her from a feeder store, so she wont come from calling her.. does anyone one know any tricks?? Any special foods they can smell a mile away? Im not worried about the rat starving or getting thirsty, there is cat food out.. but ugh the kitten :( im too worried to sleep..