Program froze and I force quit. How do I retrieve?? How do I save?

I highlited text that had saved before today (I can't find a save button anywhere but somehow it saved my work). I had to force quit because the program froze. Now I have lost everything (today and work prior to today). These were notes for an exam in 5 days. How do I retrieve?? How do I save? I use a MacBook Pro.

[title edited for clarity and brevity by moderator}