Tracking

While using the track on my iPhone in WY while hunting deer it worked great. As I became more comfortable I trusted the app more & more , it did not let me down.  After returning home to find my bull went into the neighbors 1200 acres, so on the quad I went. Checking the tracking about every 10 minutes.  When done looking off the back of the quad I notice that a large section of the track was missing , glad iI was able to follow my tracks out....any Ideas. I now I did not touch anything on the phone