That Was Yesterday by Steven Curtis

In an amazing turn of events, a nine-year-old boy profoundly changes the lives of four adults and an abandoned dog in the course of one day. It's the day before Christmas, and in a desperate attempt to remove him from a violent living situation, his aunt puts him on the Greyhound to Reno to live with the father he has never met. With nothing more than a few belongings and a note with his father's phone number pinned to his shirt, his aunt bids him a tearful farewell.