So, big presentation pending. Didn't like a change I made to a slide and I'd already saved the updated version of my file.
I decided to give Time Machine a whirl. Let me point out that I've gotten much better at keeping back-ups and taking advantage of back-up services available at work. I have clones of drives, I have back-ups of just data (docs, jpgs, etc.).
I just needed the file from approximately 2 hours earlier. Time Machine was utterly easy to open, scroll back 2 hours within my hourly backups, find the document and "pull" it forward. It was a little confusing at first because it wants to know if you want to keep the original file, the one you retreived or both.
Since I didn't actually know which was which at the time I just selected both. That allowed me to look at the files and determine which one I wanted and which one to trash. Pretty darned easy, quick and painless.