John was always an intelligent sort, although he never brought enough equipment with him to survive out in the wasteland. Moira Brown told him as much. He was recently mauled by death by vicious dogs. A quick search of his body reveals a note about treasure buried somewhere near the Scrapyard.
John can appear in the wasteland more than once, carrying a new note and a new copy of the key each time. [platforms tag needed]
John has no fixed appearance. [platforms tag needed]
It is possible to save John from the dogs, especially if you fast travel and appear right at their location, but after saving him he won't engage in dialogue, he'll only tell you to "Move on", and "He's not looking for trouble", etc. If this happens, he will appear as "wastelander", and he will still have the key and the note in his inventory. [platforms tag needed]