And then I learned about GREP.
I was looking for references to “Subtotal” on the front end, so I entered terminal, SSH’ed in, cd’ed to /app/ and entered this line.
grep -rn "('Subtotal')" .and a long list appeared. One of the files was titled Totals.php and I knew I hadn’t modified it before. When I modified the line in that file, it did exactly what I wanted!
Long story short, don’t modify core files like I did, and use GREP to save time.