How do I unmount the SD card on Android 4.0?
To protect your External SD card’s file and directory structure integrity, it should be unmounted before removed.
To do this, tap Menu > System Settings > Storage > and under ExtSD card tap Unmount SD card.
This best practice is not always followed by most users, and generally no data loss occurs. When this does happen, the Cruz may attempt to save lost data to a folder called LOST.DIR. This folder generally has useless data.