Good questions. I posted the above as it appears on the website.
I do not know why police believe that the call was a hoax. Personally, I feel that the caller was the one responsible or involved in her disappearance. Obviously the information about a family emergency was a lie - possibly meant to allay suspician about her absence for a period of time.
The bits of information posted always beg other questions. For instance, "Her last entry in the nurse's log book was at 1:50 a.m...." Does this mean she left work about that time? What were her shift hours? What kind of log entries did she usually make? Were they hourly, or just as things happened? The statement does not tell us when Donna left the Cassino.
Here is another example; "... her car was found parked at her apartment complex in nearby Stateline..."
So did she normally drive to work? Were the keys in the car? Her purse, clothing, etc? Again, the statement does not tell us much.
And Items belonging to Donna found in a grave??? Were they actually hers? Was the "grave" found where "Zodiac" or some caller said it would be? How thoroughly was that area searched? Could it be that a killer buried her in a secluded spot, and then decided to bury other items of hers nearby to get rid of evidence? Maybe the police stopped looking after finging the buried objects...
There probably are other clues which the police investigators have regarding Donna's disappearance, but have not released.
Regarding the "Zodiac" letter, it could be a number of different scenarios, as I have mentioned in a previous post in this thread. It is interesting that Donna Lass was previously employed at a hospital at the Presidio, in San Francisco, CA. - near the Paul Stine murder site. Some feel that there was more than just a coincidence in Donna's disappearance and Zodiac's aparent interest in her.
But I don't recall there ever being any confirmation of the Zodiac connection, other than researchers connecting it to his "Peek through the Pines" card.
Seems to me if it had been Zodiac the phone call would have been more
direct and he would have simply taken credit, as he liked to do.