Using LibreOffice Version: 4.2.5.2. Calc
I guess everyone except I knows that one cannot save multiple worksheets inside a .csv file (unlike a spreadsheet). I just learned the hard way after editing a file for several hours. So all my work is lost. My fault.
What fooled me was that I was able to save versions of the .csv file in different worksheets, so I thought I was backing up along the way. LibreOffice pleasantly allowed me to save the different worksheets, and displayed the worksheet tabs and names at the bottom the same as if it were a spreadsheet file. But when I closed and reopened the .csv file, all the worksheet tabs were gone, along with hours of work and my sanity.
So this is a feature request. To prevent others from repeating my mistake, perhaps have LO fail faster and more gracefully, such as refusing to save a separate worksheet and offering a warning. Thank you for your consideration.