I've tried this before. It never works for me. :[
Instead, what I do is pretend that I am looking for them to ask them a casual question. You know, like just call their name out like you need to ask them something. Eg: "Elizabeth? I need to ask you something..." and while I do this, I walk through doors as if expecting to find them in there. They usually appear and ask me what it is I want. :]