I once found a recording of a lab session in high school physics. A day I completely forgot about. A moment that had no bookmarks in my brain.
Other things about that day were surfaced. How my braces felt and the fear I felt about forgetting a textbook.
All real, but unsurfaced until then.
That makes sense considering that human memory is strongly based on associations. Activating nearby memories can bring things back.
If you hear the first tones or words of a song you're much more likely to be able to tell the lyrics that follow compared to being asked to say those lyrics based on the title.