Will a cat forget about a kitten that she moved?

my cat her kittens a little over a week ago and i have them in a box. she hasn't ever picked one up but i work up this morning and there was one missing. i looked every where and cant find the kitten. could she have forgotten about it? would she BARRY it under clothes or anything? im very worried someone please let me know. and ive been watching the mother and she just lies on the floor. she doesn't look for the kitten. please help !!! this is her first littler and this is my first cat that had a litter. im very worried. !!!