Well data liberation doesn't say that they have to act as a drop box for you. If you have full control of your music to begin with to upload, that's pretty much liberated by the very definition of the term.
Well, you uploaded them in the first place, which means you had a copy at some point.
Don't delete that copy.
Well I was hoping to use Google Music as a safe place to keep my music instead of having to keep them on a hard drive some place.
Music Plus extension for chrome allows you to retrieve tracks, and I'm quite sure there is an equivalent for firefox. It's not automatic, but it's something