Actually, I didn't unzip anything when I downloaded the Arduino software. It came as a .dmg that simply has the Arduino icon, my applications folder, and a driver that I apparently don't need because I'm using the UNO (I tried anyway after a while and it changed nothing). You drag the Arduino icon over into the applications folder, it copies real quick, and that's it. When I search my computer as a whole and the files within the Arduino software (by right-clicking and selecting "show package contents") there is nothing named sketch or sketchbook anywhere.
I really appreciate your help. Please keep coming up with ideas. I'll try anything!