This 2019 article is seeking information on Sandy's father, though it states that he is not a suspect and LE simply wants to find his friends and associates. I can't imagine that the father is not at least being considered as a suspect. Sandy's father died in 1999, so he couldn't be questioned about the murder of his daughter.
Sadly there don't seem to have been any updates since 2022.
Cold case gets new life thanks to DNA evidence
ILWACO — The Clark County Sheriff’s Office has identified skeletal remains found more than three decades ago as Sandy Morden, who went missing in 1977 when she was about 15
