I hadn't come across this missing person's case until today. As best as i can find it, this is the timeline of events on the day he went missing (taken from OTS News 11 October 2018):
• Adam went missing from home in Marshside, Southport on Thursday 9th August 2018.
• He drove to a shop in Ainsdale, Southport around midday on the 9th and returned home about an hour later. (No CCTV is available.)
• The car (a red 5-door Ford Fiesta) was still outside the house just before 4.00pm. We understand Adam then drove at some point to the RSPB nature reserve car park on Marine Drive in Southport.
• We aren’t aware of Adam having been to the car park before but he may have been there in relation to his studies as a geography student at Edge Hill University.
• He had a brief phone call and text conversation with a friend around 6.10pm. This was in the vicinity of the RSPB car park but can’t be pinpointed exactly due to the position and number of phone masts in the area.
• Some time after the phone exchanges Adam’s phone went off and has remained off since.
• Dashcam footage provided to the police places the car at the car park at 6.30pm.
• The car was found at the car park at 7:00am the next morning, Friday 10th August with no sign of Adam. Soon after, we reported him missing to the police.
• There are no CCTV or other cameras at the car park, but police have carried out wider CCTV, mobile phone and other enquiries.
• Police, together with the Coastguard, Merseyside and Lancashire Fire and Rescue Services, Merseyside Search and Rescue and Southport Lifeboat have carried out extensive land and open water searches.
• We didn’t see Adam on the day but believe he was likely to have been wearing blue or black skinny jeans, a white or black t-shirt, possibly a burgundy hoodie, and suede trainers.
• We believe that Adam may have been carrying a navy blue Adidas rucksack, and had his glasses with him.
• There have been various unconfirmed sightings of Adam both locally and around the country, but as yet none have led anywhere.
• Adam’s phone, financial and social media activity have all been checked.
There were also unconfirmed sightings of Adam on the day he went missing (BBC News 20 September 2018):
Police searching for student who disappeared more than six weeks ago have revealed details of "unconfirmed sightings" of him around the time he went missing.
The 20-year-old from Southport has not been seen since 9 August. Police said he was seen twice with a man at the RSPB car park in Marshside, where Mr Seaton's car was found. Another witness said the car was parked by another car containing two men, said to be regular visitors to the car park.
The second car was black and the two occupants are believed to be Polish, the witness told Merseyside Police. In the first sighting, Mr Seaton was seen with a man sitting on sand hills close to the derelict sand factory next to the car park, around the day before he was reported missing. In a second sighting on 9 August, made by a different witness, he was also seen with a man at the car park.
The force has scoured CCTV and conducted widespread searches at land and sea.
Mr Seaton's father Andrew said his son was "very sociable, personable and a real family guy and a bit of a homebird in many ways".
Det Insp Jackie Guinness said it had been an "extremely distressing time" for the family. She added: "I'd like to stress that these are all unconfirmed sightings of Adam but our inquiries remain ongoing and I would ask anyone who believes they have seen or spoken to Adam, or anyone fitting his description, since 9 August, to contact us."
I don't believe there have been any other sightings of Adam since the 9th August, the day he went missing.