Regarding what Donald saw on the phone: had he ever described what he saw to any law enforcement? Maybe a clue as to where Heather may be, but what happened to her? Or is it because there is no hard evidence, it can't be investigated on? I wonder how much Nancy knows about the picture he saw ...
I believe it is implied that he did describe the photo but it can not be entered into evidence based on hearsay. He can't produce the photo. The LEO can't produce it. So, he can say what he saw and how he saw it but he can't say what SM said or describe the photo. Hence the question of "In your opinion, did it look like Heather Elvis would ever come home to her family?" and his answer of no implies she is deceased in the photo without saying she appeared deceased.