But the only source for that ¼ mile distance is RT, who may or may not have paid strict attention to where he last saw Barbara. After all, he didn’t know it would be the last time. People vary a great deal in their ability to calculate distance (knowing your own pace-length is helpful, then counting - but no one does that if they believe their spouse has merely walked on ahead a short distance).
He admits that he panicked when he didn’t see her at the RV. He then looks around (coming back and forth to the RV from where he thinks he last saw her? Did he ever second guess that location? Does he use his own pictures as reference points? He doesn’t mention that kind of activity, he mentions hollering and going to a cave they knew about and waving his arms, but he doesn’t mention using his pictures to make sure he had the right starting point for all this activity. I’m not criticizing him, I’m just mentioning that in his panic, he may not have been absolutely accurate about exactly where he set off to take the pictures.
I don’t think RT left the area at all that night. In theory, LE used RT’s pictures to get some indication of this last sighting, but if RT walked further towards rocks he decided not to photograph, or did a little exploring before turning back toward the RV, the pictures would not show this. So the time factor would still be unknown.
I can think of many scenarios in which couples separate on hikes. RT has never given a clear indication of what Barbara’s mood state was when she decided not to join him in walking to that particular rock formation (which should be the last picture of the day, according to what he said).