Let's not assume we know the nature of the therapist/client relationship with respect to what would be a red flag.

My therapist knows me well enough to know that if I started showing up at her work, etc, something was going on emotionally for me and that I needed her. More than likely, she'd feel sad for me and try to work through it. She'd probably also let me know that I need to call her and make an appointment if I'd like to see her. I don't think she'd jump to the conclusion that I was some sort of dangerous stalker.