I don't mean literally seized, but rather "tapped on the shoulder" or just called as you are walking somewhere (when it's not your class time or office hours). How did you respond?
Perhaps your students respect your personal space. Nowadays, students approach me anywhere, any time, and ask me to give them a moment's attention, which I always do, unless it's going to make me late for class. (It's certainly made me late for everything else, though!)
Back when I was a TA for CS 125, Introduction to Computer Science, at the University of Illinois, students used to literally grab me from behind. One time, I shrugged it off reflexively, and the student recoiled, realizing it was something he shouldn't do. I said as much. Another time, a (male) student followed me into the men's washroom to ask a question, and I had to explain that this was not quite fair to some of the students.
Maybe I'm not being emphatic enough...