The point I tried to get across before is that the office complex is the natural default
place you'd expect to find the project supervisor. Granted, Scotty's a hands-on type, but if you're in charge of the project and have to do administrative work, it stands to reason that you'd spend a lot of time in the offices. So as a rule, I don't think Scotty being in the office complex is any stranger than Kirk being on the bridge in a typical TOS episode, or Sisko being in Ops on DS9; it's the home base for the person in charge of the whole operation, so it's not a surprise to find them there.
So there would've been a pretty good chance that Scotty would be there at any given time, and since he would've gotten the revised departure orders just minutes before Kirk arrived and would've had to scramble to respond to those new orders by working up a new strategy, he probably wouldn't have had time to finish up there and go anywhere else before Kirk arrived.