I read the article and noted that while it was highly relatable, it was more relatable on some things than others. Then I noticed that the article is from U. of Alberta sexual assault center. The content that is written would make sense in light of that. Seeing trigger in terms of clear incident or incidents that produced PTSD.

But as ElsaMars points out, it's not always that obvious where trauma stems from.

You mention being trapped. Whether or not it was light or dark may not matter. You want to leave the situation, but are feeling trapped (if only by social convention). Then whatever emotion causes you to want to leave is amplified by then feeling "compelled" to stay and endure it.

I can't say definitively if that's a trigger or not, but I do think that the article -- while excellent -- could maybe be a little narrow in describing trigger simply because of where they're coming from.