I guess I was mistaken. I thought I remembered her father saying the kids were with Dad. Maybe what I'm remembering is that she lived with her parents. It's been a really long day after an insomniac night. Sorry.
My understanding is that the father had the kids Thursday through Sunday. I don't have a link to back it up, but I am 99.999% sure I read that. Then, when it was supposed to be her days with the kids the next week, the father kept the kids so they would not know she was missing.