Hello, have you been able to obtain any of the law enforcement reports? This can be helpful in having a starting point to things like where your father was found deceased. It can also be extremely distracting to put stock in psychic mediums that operate in unverifiable uncertainty.
In the autopsy report, what did they identify as the cause and manner of death?
First, I am sorry for your loss, Did he by chance have a phone, earbuds, smartwatch, or iPod that he may have had on him? Have you been able to track phone records, ping locations, and activities? You may be able to look through the phone for an app to track any one of the smart devices. Try looking at the latest contacts and see the last conversations, any meetups, or the pings for a timeline or the latest whereabouts. You may be able to try it on one of his older devices or google if you know his username and password.
I agree, Did he have a life 360?