When Donna Lass began working at the Sahara Tahoe Hotel & Casino in June 1970 it would have been her responsibility to supply the casino with her contact details (phone number and/or current address), and encumbent upon her, to acquire the contact details (phone number) of the casino in case she needed to ring them in the event of unforeseen circumstances, such as an illness to herself, family illness, accident or medical emergency By September 6th 1970, this most certainly would have been done. If Donna Lass had really received an urgent message from her family because of an illness, what would have been the appropriate response - waste valuable time trying to locate her landlord, Nick Davis, asking him to ring the casino on her behalf - or simply making the phone call to the casino herself by using a public payphone or asking to use her landlord's phone? If the relations of Donna Lass did have an illness in the family and only had the phone number of Nick Davis by way of contacting her, he would have then made contact with Donna Lass, who would have rang her family back enquiring about the gravity of the situation, before contacting the casino. Any phone call received by Gordon Petrovich of the Sahara Tahoe Hotel & Casino, on behalf of Donna Lass, makes little sense. The only person who had anything to gain by reporting a family illness on behalf of Donna Lass, is an individual who knew that Donna Lass was incapable of making the phone call herself, because she was either under duress at the time, or dead.
Donna Lass had just moved into the Monte Verdi apartments, so how likely is it that the family of Donna Lass had the phone number of the landlord, Nick Davis, to even ring him about a family illness? And even if they had, why would Nick Davis bypass Donna Lass and inform the casino of the family illness himself, rather than informing Donna Lass of the family illness and her taking responsibility in notifying the casino?
The mysterious phone call using the name of Mr. Davis, which he denied was him, must have come from a murderer familiar enough with Donna Lass to know the name of her landlord. Another question that must be asked - is how many people (then or today) would know the name of their friend's landlord? Taking into account that Donna Lass had just moved into the Monte Verdi apartment complex, there may have been some friends that would have known her plans, but how many of these friends would have known that her landlord was called Mr. Davis? One such friend (or casual acquaintance) that may have been privy to this information, would have been somebody who lived at the Monte Verdi apartments themselves. Possibly somebody who informed Donna Lass previously that the Monte Verdi apartments were a good place to live. Often, people move into future premises on the recommendations of others - usually friends they trust.