Okay, I have to take back everything I and others said about what triggers Mister X in the B scenario. It's neither the S.T.A.R.S. office nor a specific item in it, it's the corridor itself (where you first encounter a licker in the A scenario). When you approach the corner leading to the linen room and the unicorn statue, Mister X will come around this corner, whether you entered the S.T.A.R.S. office before or not.
But the thing is, you don't actually have to go there yet. The linen room is locked anyway, and the unicorn statue room can also be accessed through the library. The next time I play a B scenario, I'll get what I need from the S.T.A.R.S. office and return the way I came, just to see if Mister X shows up at all before I return from the basement.
But the thing is, you don't actually have to go there yet. The linen room is locked anyway, and the unicorn statue room can also be accessed through the library. The next time I play a B scenario, I'll get what I need from the S.T.A.R.S. office and return the way I came, just to see if Mister X shows up at all before I return from the basement.