Loss of data moving files to memory stick

Did you stop the memory stick before you removed it? Right-click and then there should be an obvious option (I think called safe remove).

This sounds like you're not unmounting the memory stick before removal. Linux caches file writes in RAM, and so even though the files look to be on the memory stick, they have not yet been written, You must unmount the drive to ensure all pending writes are written to the memory stick.

To unmount, right click on the file browser window, and choose "Unmount Volume".

Dear Ubuntu Friends, I write because I have an error on my ubuntu, is a grave error.
My computer is an OKI NB0108 has a SD card reader. I do many pictures and videos for a web page I have on a locality. The error comes when I put the SD card in my computer with Ubuntu, and when I give a copy to all content, and I keep a folder on my Ubuntu system, instantly disappears entire contents of my SD card, alone on the folder you've saved. Already happened to me ten times, and when I try to recover with recovery software is unable to recover all the content. I hope that since ubuntu is to review the situation, and find which is the bug that causes it to erase all data on the SD card and make them go away completely without chance of recovery, nor are stored anywhere on your hard disk where I have installed Ubuntu. I hope they make all the necessary steps to repair this situation. So far I have had to change the operating system until you solve this problem in Ubuntu. I tested with different SD cards of 1, 2, 4, 6, 8, 16, 32 GB and all data is lost in a unrecoverable.

I hope you will manage and arrange everything properly. Greetings.