Thanks for your replies. I appreciate the feedback. I have a few follow-up questions.

1. Does talking to a flight attendant after de-boarding count as disobeying a crewmember's instructions? I politely raised my concerns after everyone has de-boarded, and the two people (the pilot and the flight attendant) made me feel very threatened. Can I sue for threatening me?

2. Does the protocol for not letting someone back in if they were out of eyesight of the crewmember actually exist? A long and frustrating Google search does not seem to yield anything, and I would like to see the full protocol, if possible. I just don't think that the actual protocol says that you are supposed to stare down at the person, refuse to let them enter the plane, but at the same time keep their belongings in the plane.

3. I'm also trying to assess how outrageous (or how typical) this situation was, and what course of action I should take next. I guess I just felt that no one was interested in helping me. For example, when I went back to the gate agent asking her to verify that I was just getting a tag from her, she said that she was "busy with closing the flight", which set me in further panic mode, as all of my stuff (except for my cell phone, which had my boarding pass in it) was still on board. Should I just file a complaint and let it rest? A complete account of what happened on this forum? Should I be seeking a lawyer?