Lightroom: I did save to catalog and I lost my changes; can I restore my changes?
I'm not sure what "save to catalog" does.  In fact I couldn't even find the command anywhere within Lightroom 4. I always import batches of photos directly into LR straight from an SD card. This automatically adds them to the catalog and saves the raw file in a separate directory.

The catalog is just a database which contains all the edits you do to a photo.  Any changes you make while editing in the develop module are saved the instant you make them.  You can also save the changes as XMP data which is written directly to the raw file so if your catalog ever becomes corrupt your edit data is saved.  There is an option to automatically save xmp data or you can do it manually on a photo by photo basis.

If you use Time Machine or another backup system you should be able to go back and restore to any saved point.