There cannot be evidence of the first, but there can be evidence of the other two (supposing one of the latter options happened). The problem is that there cann

There cannot be evidence of the first, but there can be evidence of the other two (supposing one of the latter options happened). The problem is that there cannot be evidence that those two didn't happen. So if the first option happened, we can never be sure of it; the only way of being sure of something is if one of the other options happened and it is revealed.