Two more prodigal cat tales:
My cat Mary, before she moved in with me, apparently disappeared for three months from the feed store where she had been living. When she returned, they could see that she'd had a litter of kittens during her walkabout. Perhaps your cat is just sowing her wild oats.
When I was three or something, our cat Fluffy (a rough, battle-scarred, unneutered male) left home for a long stretch and then walked into our kitchen one night, looked horrified, and took off forever. At least we knew he hadn't died; he just hated us.