I’m not sure hiring a PI would help anyone here as I think the police have done a good job piecing his movements together with the CCTV footage I don’t think a PI would help them get the answers they’re looking for, I think the main working hypothesis for the police is that he fell into the water and this as horrible as it sounds becomes a waiting game until the water gives up the body.
With the police scaling back their search efforts I wonder if there’s something in the background that suggests to them he could have intentionally entered the water IE mental health past issues, google searches. Him leaving his card at the side could have been a ‘sign’ for his family that this was where he entered the water - abit like Gaynor Lord who left her coat at side of the river before entering. All MOO of course.