The GPS device a Washington State visitor had in his backpack for a hike at Devils Lake was a good thing to have, until it went off accidentally.  The false alarm happened Thursday afternoon and prompted an emergency response phone call and search for the man and his two sons.  The coordinates for the alleged lost Lance Peterson, 41, of Battle Ground, Washington, pointed to an area of the Devils Lake trail about 1 ½ miles from the lake.  Emergency officials spoke with Peterson’s wife back in Washington.  She said her husband was hiking in the area with their two sons, ages 11 and 13.   And they were planning to climb broken top and south,  Sister during a four-day trip.  Attempts to contact Peterson by cell phone and text message were unsuccessful so a SAR team headed to the area.  They located the surprised trio several hours later, that's when they discovered the device had accidentally triggered in the backpack.