Thanks for the help, david_e!
I got so excited for a second, especially when I looked in Applications and saw I had Time Machine, so I opened it up, and it just said to set it up and had a little slide button showing it's turned off.
I know I mentioned way above but I'm not tech savvy at all. It's one reason I love Macs - on the whole so much easier, more non-techy-user-friendly and more intuitive to deal with. I'd heard the words Time Machine before but wasn't really sure what it was - honestly I thought it was some separate device to buy - so I didn't know there was any way to set that up on my computer.
Now that I know I can and could've, on top of the irony of the timing of these being deleted right before I figured out how to save note files separately and also apparently just before the introduction of this new Evernote thing or whatever that saves notes outside of the Reader software, I feel like I'll need to devote at least a good week or two to moping around about all this!