Another day... no Brian!......
Everyone seems to be in on this hunt, the FBI , the CIA, the Army, the state police, the adventurous Mr. Dog, ( It took me 32 threads to figure out that DTBH meant this hardy chap ) so I throw in the foundation of Sleuths, Mr Holmes, Sherlock to his friends. And his oft quoted homily to all sleuthers out there..
'When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth."
quote from "The Adventure of the Blanched Soldier", a 1926 Sherlock Holmes short story.
All that seems to absolute at this time, is... the last people to see Brian alive ( and it's not as if they put it like that, their story is he just sort of went 'missing'...one blink and lo! no Bri! ...)....are his parents.
That is the very last time, and the very last people to see Brian walking and talking. ..
The last people to be in contact with the person searched for are usually high on the suspect list, for very good reasons...