I’m using PopOS 19.04, although the issue was also present on vanilla Ubuntu 19.04 and caused me to lose some important files.
Whenever I use a flash drive for Linux, format it as ext4, add files, and then remove the drive from the USB port, all of the files disappear. The only way that I have recently found to make them not disappear is to right click and hit “remove safely”. I can do this every time if I have to but I don’t have to do it for Windows, what is different? Is it just a bug?