A USB stick stands for information carried in a small, easily lost form. It is read as memories or secrets kept close, or as the worry of misplacing something important.
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.