There's lots of evidence that sniffer dogs aren't particularly reliable. Andrew Taslitz, professor of law at the University of Pittsburgh, published a comprehensive analysis of the use of canine evidence in North America in 1990. He concluded that such evidence is imbued with mythical qualities about a dog's abilities and is likely to be overvalued, misunderstood and misused by jurors. Dogs might accurately follow a scent sometimes, but certainly sometimes they do not.
The lead detective has stated that
1) the construction area was at a level below the Saloona
2) the construction area 'was only boarded up by the doorways with chain-lock plywood doors' and 'somebody could of squeezed in or out...'
3) 'the basic indication is that somehow Brian got down into the construction area'
Now, since the bar closed around 30 minutes after Brian was last seen on video, if the detective is right, that would put Brian in the construction area within a matter of minutes of his last being seen alive, and within minutes of the point from which all signs of life - phone use, card use, walking past a cam, using apt, etc., absolutely ceased.
The detective also noted that
4) the construction area was 'completely dug up'
5) the construction area would have been difficult to navigate even by a sober person
To me, this all strongly suggests that Brian's disappearance is linked with his coincident appearance (if the detective is right) in the construction area.
A person disappears without any trace for going on 12 years at the very same time he is believed to have inexplicably entered a dangerous, dug up construction area?! Probably more than just a coincidence, IMO.
Now, the detective also stated that Brian
6) '...most likely got exited out of there (the construction area)'
The detective must believe that not because there was any subsequent sign of life (there was the phone pinging off a cell tower, but Cingular dismissed that "Cingular told police that Brians phone had never actually rung, that it was an equipment glitch on the companys end"
http://www.gossiprocks.com/forum/news/27915-waiting-brian.html ), but because Brian was not found in the construction area.
But it may well be that Brian's remains are in the construction site and searchers simply failed to locate them.