An educated guess is still a guess when there is no body. PF picked up his daughter on Thanksgiving. Where is the proof he also murdered her mother that day?
JMO
I think if you had her phone records and every other day for the past 5 or 10 years she had, say 5 to 25 calls on her phone, and after 11/22/18, she had zero, that would be indicative that she was gone. if there are other periods of silence, then maybe not so indicative, but if she has always been communicating previously, the silence is remarkable.