The Monticello Card was postmarked July 13th 1971 and Kathy Bilek was targeted and murdered in the Villa Montalvo woods in Saratoga on April 11th 1971. Therefore, a Zodiac Killer stating "shought victim 21", would be referring to a victim he targeted 94 days ago. In other words, he "shought" Kathy Bilek on April 11th 1971. This total of 21 would fit correctly in the Zodiac Killer sequence, because he claimed 17+ victims on March 13th 1971 when he mailed the Los Angeles letter. Let us apply this template of 94 days to the disappearance and murder of Donna Lass on September 6th 1970, to discover whether the "sought victim 12" would now fall into line with her being targeted in the Bay Area when she worked at the Letterman General Hospital.
If we deduct 94 days from the date of her disappearance on September 6th 1970, we get June 5th 1970 - the exact day she prepared for her move to South Lake Tahoe to begin work at the Sahara Tahoe Hotel & Casino. Was the Zodiac Killer effectively hinting that he had "sought" Donna Lass as victim number 12 in the Bay Area, but she had moved from San Francisco on June 5th or 6th 1970, thereby thwarting his plans? The April 20th 1970 '13 Symbol' cipher claimed 10 victims, which wasn't updated on the April 28th 1970 Dragon Card. The June 26th 1970 Button Letter had claimed 12 victims. Therefore, if Donna Lass had been "sought" as victim 12 by the Zodiac Killer, it would have fell somewhere between April 28th 1970 and June 5th 1970. Effectively, we are looking at the preceding month (May 1970) to when she packed up and left for South Lake Tahoe. This month could be pivotal in revealing the identity of the Zodiac Killer through the circles of Donna Ann Lass. Who were her close friends, colleagues or 'admirers' during this short window of time?
Through alliances with the Monticello Card, the Pines Card was almost certainly a Zodiac Killer offering - and therefore inconceivable that the phrase "sought victim 12" was simply a 'schoolby error' on behalf of the killer. Equally, a copycat with even the remnants of a brain, couldn't have made such a nonsensical mistake having made all the effort to mimic a Zodiac Killer communication in the first place. It wasn't like he was short of newspaper coverage. The retrograde step of the victim count to 12, in combination with the past tense of "sought" certainly wasn't a mistake - it was chosen for purpose. Possibly the day the Zodiac Killer's plans were scuppered as Donna Lass upped sticks and headed out of state to South Lake Tahoe.