lost apple watch

My girlfriend has lost the apple watch she had gotten from me for Christmas, when she tracks it on the app, it takes forever to repin it's location but when it did, it would say it's in her car. When I tell you I have ripped that car to piece and have not found anything close to an apple watch. I don't know what to do. I'm trying to find out if it's under warranty if I can get a replacement or what