Turn it on.....when it has got signal find mark or waypoint and put one at your position,name it truck,camp or whatever is applicable.
at any major deviation from course or feature you pass put another in.
heading back search nearest waypoint and go to or navigate to.....it will give you a bearing. Use your handheld magnetic compass to follow bearing to way point checking occasionally as you drift off course picking the natural easiest path and so on.
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