Being shut in a room you cannot leave is read as feeling boxed in by a situation, a rule or a role. Tradition notes whether someone else turned the key or whether the door was yours to open.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.