Is there a a way to convert a css file that has been saved by accident in non UTF-8 format and now only shows up all on one line??

The question is simple and most people have encountered it at one time or another, but I can't seem to find any answers or even discussions about what happens when it's saved incorrectly and if there is a way to fix it or change it back....other than backups.

I've been designing for years and have luckily never done this before because I always keep good backups and procedures, but somehow, I don't even know how, the file saved with all of the text on a single line! And of course the one time I've ever done this, and it's on a file that I spent hours changing major CSS designs and somehow didn't save a backup.

Also, what are all of the reasons for something like this happening, because I've never actually learned how it all works precisely and I would like to figure out what I did wrong. And to make sure I didn't screw up any other files on a site in the past few days of work! I use Notepad ++ usually and know the differences of how Notepad, Wordpad, Notepad++ ....and this file displays all in one line in all editors. This site is on a server I've never used before and I'm building in Wordpress which I rarely use. What are all the factors which might change the encoding down the line? (ie text editor, ftp software, server, cms, etc etc). I haven't had this happen very many times so I just never learned it.