A bag is read as what you carry with you every day — identity, worries and private things. Losing it traditionally stands for a fear of losing yourself or something essential.
When this appeared in your dream, what were you feeling?
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.