The following facts are known about the girls' disappearance:
Francine was reported missing on 16 December 1978; Kerry was reported somewhat later.
Makeup that the girls had been applying was found left out as though it was going to be used again.
They were reputedly maturing into being interested in boys.
The girls showed up at El Molino HighSchool and joined a group of cigarette smokers in the parking lot near the tennis courts.
Their classmate reported they had been invited to a party.
Alternatively, they were said to be headed for Coddingtown Mall in nearby Santa Rosa, and were reportedly going Christmas shopping.
Kerry was still recovering from appendix surgery. She left her antibiotics at home.
Forestville then was a five block town. Most of its inhabitants knew one another, at least by sight.
The traditional hitchhiking spot for Forestville was a gas station that is presently a package goods store.
LE believed they were voluntary runaways.
Now let's try to arrange these factoids into a reasonable scenario. I'll begin with this.
The date Kerry was reported missing, 16 December 1978, was a Saturday. That means she cut school during the previous week. With Christmas holidays pending, I suggest Friday the15[SUP]th[/SUP] as the most likely date for their hitchhike.
Given that they were becoming interested in boys, and might have been invited to a party, it seems most likely they tinkered with the makeup before they went to school, where both boys and other girls might admire them.
Makeup in place, they went to El Molino High School to join their friends in smoking cigarettes. They told a classmate they were going to cut school and hitchhike to a party, and invited her along. She declined. This report can be verified by the classmate's mention of the denim jacket Francine was wearing.
Other reports claim they were headed for Coddingtown Mall and/or going Christmas shopping.
Forestville was small enough that the girls were noticed hitchhiking from the filling station. Or so says the classmate.
At this point, I queried Google maps for package goods stores in Forestville. Lo and behold, the following pops up in street view, half a mile down the street from the school.
https://www.google.com/maps/@38.473...4!1sHy_2wY6o5VZVHJG0LSOwOA!2e0!7i13312!8i6656
This is obviously a repurposed filling station. If you click the arrow for a spin to the left, you are looking down the road that leads to Coddingtown Mall. I submit that this store was the start of their journey into oblivion. According to the classmate, they would probably be picked up by someone they knew.
There is an alternate route from Forestville to Santa Rosa, along River Road. However, it presents problems for hitchhiking to Coddingtown Mall. River Road joinsHighway 101 well north of Santa Rosa; hitchhikers then have to find aride south to Coddingtown Mall. Laid out atop an old railroad right-of-way, River Road is a highway of sweeping turns; drivers move right along, with little impediment to speed. River Road grazes the north edge of Forestville, and is a major thoroughfare for the denizens of Guerneville, Monte Rio, Jenner, and vicinity. There is little likelihood of being picked up by an inhabitant of Forestville. FWIW, in the mid-1980s, I used to regularly commute along River Road out to Monte Rio, and cannot ever recall seeing a hitchhiker. River Road, then, was an unlikely route for the girls.
LE assumed the girls had run away. Much less attention was paid to missing children back then. If the local deputies knew of other Graham children running away, it may have seemed to be more of the same. However, the makeup kit was left out, and Kerry did not have her antibiotics with her when she left. Then too, Christmas was nigh. What kid wants to miss Christmas?
Sources:
Wikipedia:
https://en.wikipedia.org/wiki/Murders_of_Kerry_Graham_and_Francine_Trimble
Santa Rosa Press Democrat, 15 February 2016:
http://www.pressdemocrat.com/news/5...rs-never-told-forestville?ref=menu&artslide=0