I had this on my last punt last week. I was there a literally one or two mins, and the door went, and another girl went out to answer it. I saw a bald guy hanging about the the block before I entered and headed for for the apartment, so I guess it was possibly him.
It really doesn't bother me if there's another guy in the apartment, as they're just there for the same thing as what I am. Personally I'd find it a little awkward if they entered of left at the same time as me though.