In your context bob is with a group. The group knows where bob is. THAT is the important distinction. As someone lost you KNOW you are known to be lost AND h

In your context bob is with a group. The group knows where bob is. THAT is the important distinction. As someone lost you KNOW you are known to be lost AND have an idea where others SHOULD be looking for you. AGAIN, my advice is for the inverse of this context, where you must report your self as 'lost'.