Well, if you've ever been to a commercial construction site when they are going several stories down for footings, pilings, maybe a parking garage, etc., it is not hard to see how a body, if it landed in wrong spot in trench along a footing a wall, might be inadvertently buried when trench is filled in, especially in rainy, muddy conditions. Yeah, seems a bit unlikely, but all the alternatives seem wildly unlikely, IMO.
There's a reason there wasn't a single trace of Brian after 1am or whatever that morn - he was dead. No ATM use, no calls, no nothing. He was already dead. Some would drum up a murder scenario. To me, accidental fall or intentional leap followed by inadvertent burial in a construction trench - not one across town but right next door - is far simpler and more likely. Had there not been a construction site right next to the structure in which Brian was last seen, I would not have posited this theory. But there was apparently a construction site right next to where Brian was last seen. And if surveillance vids are to be believed, only way Brian got out of the building was via the construction site. And things get buried in construction sites - pillars, walls, footings. And once buried, they're not seen again for many a year. If ever...
I always tell people to do their own research but from the info the I have been able to gather mainly from watching interviews with detectives every exit had cameras on them either directly or indirectly from cameras from other buildings. So even the construction area door was covered. I personally have said before on here I think he jumped over the patio onto the roof of the restaurant under the bar and left from there, but I'm not putting any money on that theory either.