I have videos and music on the SD card inside my Android Moto G5 phone. I wanted to watch some of those videos on my Android Lenovo A10-70F tablet. So, I turned off my phone, removed the SD card, and placed it into my tablet.
The tablet asked if I wanted to have the SD card only work on the tablet, or use it as portable storage. I selected the portable storage option, and the file browser immediately popped up. I was horrified to find that the SD card was reporting itself as only being 1% full, and the only data inside was in LOST.DIR and a single album in /music (which is the first album alphabetically in my collection).
Moving the SD card back to my phone hasn't changed anything. Have I really lost all my media?